The twin horses reared up, their massive heads reaching a hundred feet into the sky, their metal skin glinting in the sun.

"They're magnificent, Doctor!" said Jamie, staring up at them. "It almost feels as though they're actually moving."

The Doctor gave an indulgent smile. "Yes, I rather thought you'd like them."

The two were standing near the entrance to a canal, and above them rose a pair of enormous sculptures, each one a heavy horse's head clad in scales of angular metal, one with its nose to the sky, the other with its head dipped, both looking impatient to get moving.

A thought struck Jamie and he stepped back, clutching the Doctor's sleeve while keeping his eyes on the sculptures.

"That's no why we're here, is it, Doctor?" he said, pointing up. "Yon horses aren't about to come to life and terrorise the people of Falkirk?"

"Jamie, no!" said the Doctor, laughing. "It's like I told you: we had some free time for once and I thought it might be fun to take in a little Scottish culture. After all, you're always telling me about the wonders of your homeland."

"Aye, well," said Jamie, letting his hand drop to his side, "I was talking more about morning mist on the heather, the sound of bagpipes floating across the glen, that sort of thing. But this -" he stopped and breathed in deeply, before turning to the Doctor with a grin, "these Kelpies will do very nicely indeed."

As they were talking, a tour group was being led across a narrow bridge which ran over the canal. Catching the Doctor's eye, the tour guide attempted to convey without words that this was a paid tour, and as they hadn't, perhaps they wouldn't mind stepping aside for those that had.

"Oh, right you are," said the Doctor, taking the hint and moving away, closer to the canal. "Perhaps we'll catch the next one."

With his dishevelled coat, oversized shirt collars and baggy plaid trousers, the Doctor may have looked quite out of place in modern day Falkirk, but most of the group only had eyes for Jamie's outfit as they passed - in particular, his kilt.

"Doctor..." said Jamie, looking uncomfortable.

The Doctor smirked. "Don't forget, they've come here for the Scottish culture, too, Jamie!"

Just then there was a splashing sound behind the tour group, followed by a startled commotion which caused the Doctor and Jamie to turn around to see a naked woman, soaked from head to toe, her long black hair plastered to her skin, pushing through the crowd of people.

"Jamie!" she shouted, pointing right at him. "Jamie McCrimmon!"

Jamie was already hurrying towards her, pulling off his jacket to put around her bare shoulders, but before he had a chance to speak she grabbed his shoulders and started pulling him backwards towards the water. He shouted to the Doctor in a panic, but the woman swung herself and him towards the canal with surprising strength, her fingers digging into his skin.

"Jamie!" cried the Doctor, but it was too late. With a splash, the pair landed in the water and the Doctor was just in time to see them vanish, as though dissolving into liquid themselves.

#

Jamie hauled himself out of the water with a wheezing gasp as he struggled to draw breath. Coughing, he rolled onto his back and forced himself to sit up. The woman was there too, kneeling in the water, her naked back hunched and heaving with exhaustion.

When he was finally able to speak, he shouted, "what on Earth did you go and do that for? Are ye mad? I'm completely soaking!"

It was only then that he took in his surroundings. There was no canal, no tour group, no giant metal horse sculptures. Instead, he was sitting in a forest, on the rough pebble bank of a wide river. While the Kelpies had been near to a busy road, here there were no sounds save for the wind through the trees and the steady rush of the water.

"Hey now, where are we anyway?" he demanded.

The woman moaned softly, barely able to lift her head, and said something which Jamie could not make out.

"Aye, and another thing - how is it you know my name when I've never seen you before in my life?"

"All the rivers of Scotland sing of your tale, Jamie McCrimmon," she said, her speech punctuated by weary breaths. "The brave Highlander who travelled farther than any of his countrymen ever have or ever shall. I asked the river for its help and it spoke to me, telling me where you stood by the water and how you spoke of the land and of Kelpies."

Jamie looked sceptical. "All the rivers? Is that right?" All the same, he found himself watching the current for a few moments, wondering what else it might be saying about him when he wasn't around.

The woman stood up then with a splash, making Jamie look up and then immediately cast his eyes down again.

"Oh! That's right. I'd forgotten that you didnae have any -" his voice trailed off and he glared fixedly at the pebbles beside him. "Look, have you no got any clothes you can put on?"

She laughed. "It's all right, you can look."

"Aye, you say that, but if it's all the same to you, I'll no bother."

"Really, Jamie, look at me."

Reluctantly, squinting until his eyes were almost shut, he raised his head.

"Hey!" he exclaimed, his eyes going wide. Before him, the woman still stood knee-deep in the fast flowing river, only now she wearing a rough-spun tunic of a deep forest green and a long skirt which appeared to have been woven from thick fronds of river weed.

He stared at her. "You're no entirely human, are you?" he said, which made the woman laugh again.

"I am a Glaistig," she said.

"A spirit?" said Jamie.

"Aye, if you like. I suppose you could call me a guardian spirit. My name is Niamh and I am eternally sworn to protect the McKinnon family and their farm." Her face clouded over again. "Only now there is only one member of that family left alive," she said, "and he is in mortal danger."

Now Jamie felt on more familiar ground. "Ah, so that's why you brought me here, to fight whatever this danger is?" He tutted, and shook his head. "You should have got the Doctor, too. He's the expert in these things, no me - never mind what yon river might have told you. And he could have brought us all here in his TARDIS too, and I wouldn't be sat here wringing oot ma kilt!"

"I'm sorry, Jamie," Niamh said. "The river spoke only of you and said nothing of this Doctor. I had no way to know you had your own means of transportation."

"Aye, well, I don't now, do I? I just hope I can find my way back to Falkirk when all this is done. We must be miles away." He shook his head again and pulled himself to his feet. "Come on, then. The sooner we get finished here, I suppose, the sooner I can figure out how to get back."

#

In Falkirk, there was uproar as the tour group crowded around the Doctor at the water's edge, trying to spot where the pair had disappeared.

"Where did they go? Did they drown?" yelled one.

"Did you see that? She didn't have a stitch on!" cried another.

"Was that for real?"

"Can anyone see them?"

"Not a stitch!"

"Please, everyone, step away from the water!" This was the tour guide, trying to take control of the situation. He pulled out a mobile phone from his pocket and jabbed at its screen with his finger. "Help will be on its way shortly. I just need you all to move back to safety."

The Doctor tried to extricate himself from the crowd who had no intention of moving, to safety or anywhere else.

"Someone has to do something right now!" demanded one of the group.

"I'll go for help!" shouted the Doctor, seizing his chance and making a break for it, running back towards the car park where he had landed the TARDIS earlier that day.

"Here, where are you going?" shouted the guide.

The Doctor turned around. "I have... something," he called back by way of explanation, "in my... vehicle, which might -" he broke off. "Oh, this is wasting time," he said to himself as he turned on his heel and set off again at a sprint.

He found the tall blue Police Box where he had left it, pushed open the doors and threw himself inside. In an interior far larger than the box should have been able to hold, he rushed to an octagonal control console and began flipping levers and pushing buttons.

"Let's see," he muttered to himself as he worked. "They went into the water here... yes, there they are - I've got a trace - and if the current moves this way... no, that's not it. Perhaps this way? No, I've lost it again. Well, that shouldn't be. That shouldn't be at all."

"They can only have gone up or down stream!" he shouted at the empty room. He moved around the console, checking screens and frantically typing calculations. "No, no, no!" he said, growing panicked. "Everywhere I look they disappear. That can't be possible!"

At last he straightened up and backed away, with a look of horror. "I've lost him," he said, stunned. "I've lost Jamie."

The Doctor collapsed into an old wicker chair. "Oh, Jamie," he said, "I'm so sorry. To think, after all we've been through, to just lose you all of a sudden after all this time!"

He sat up straight and slapped a hand across his forehead.

"Oh dear me, I've spent too long looking at sculptures," he cried, jumping to his feet and leaning over the console once more. "It's got me thinking in only three dimensions!"

He jabbed a button and then another. "There! Now, follow the trace through the water again, only this time," he reached out and turned a dial gently, "take it - back? Yes, back, through time as well."

He skipped with excitement and clapped his hands. "Yes! I've got them."

The Doctor entered the coordinates and set the TARDIS in motion, the central column of the console rising and falling. He checked where they were heading. "Gosh, really?" he said. "1792? Jamie will be pleased."

#

Jamie was not pleased. The air was growing chilly as the afternoon wound down and his clothes hung heavy and wet against his skin, refusing to dry off. Their way was slowed further by Niamh's insistence on wading through the river instead of walking along the bank as he did. He had considered, once or twice, asking why she didn't simply travel through the water as they did to get there, but he decided he wasn't in any hurry to go through that experience again, and besides, Niamh had seemed so exhausted after they had arrived it was clear that travelling that way took a lot out of her.

She was picking up now, however, seeming to grow stronger despite the hours they had spent walking.

"This farmhouse had better not be much farther," he grumbled, "or we'll have to camp here for the night."

Niamh splashed on. "We're nearly there. This river flows into a loch and the farm is right beside-"

"What is that?" exclaimed Jamie, interrupting her.

Up ahead, in the bend of the river, stood a massive horse, a good head taller than any horse Jamie had ever seen before. Its body was translucent and seemed to ripple and shimmer, as though it was made of the very water it stood in.

"Jamie, it's a Kelpie, you must hide," whispered Niamh, but it was too late. The creature turned its head and splashed towards them.

Jamie squared his jaw and adjusted his tunic. "I'll handle this," he said. "Right, beastie, be on your way now. On ye go."

"Jamie," said the Kelpie, its voice like water over pebbles. "Come to me. You are strong and we are in need of aid. Come with me and you will save us all."

"Och, how does this one know me too?" said Jamie, as Niamh tugged at his arm, trying to drag him away. "Is it yon gossipy river again?"

"No," said Niamh, "it can read your thoughts. Jamie, listen to me, you have to stop."

"Stop?" said Jamie, puzzled, and then realised he had taken a step towards the Kelpie and reached out to it with one hand.

Niamh struggled to hold him back. "You must not touch it," she said.

"I don't want tae touch it," scoffed Jamie, but seeing that his hand was still outstretched, his eyes widened. "I really don't!"

"Come to us," the Kelpie continued, low and soothing and relentless. "Come to save us. Come to help us."

Jamie's fingers were nearly at the Kelpie's broad neck. Through the creature's skin, he could see bubbles and bits of leaves swirl and dance and realised it really was composed of river water as it appeared to be. The Kelpie had a thin, pearlescent bridle around its head and, against his will, Jamie tried to grab hold of it and knew he was preparing to swing himself up and onto the Kelpie's back.

Before he could make contact, however, Niamh knocked him sideways and pulled him away. The Kelpie reared up with a cry and pawed the air with its massive watery hooves. The splash it gave off when those hooves met the river again showed Jamie that getting trampled by a Kelpie would be every bit as bad as by an actual horse.

As Jamie and Niamh scrabbled backwards in the river and struggled to their feet, the Kelpie continued bucking and splashing, letting out a keening cry that to Jamie's ears sounded almost electronic.

"What's the matter with it?" shouted Jamie over the noise.

"I don't know," answered Niamh, "I've never seen one act like this before. It looks almost angry."

The Kelpie crashed down one last time, went silent, and swivelled its head towards them.

Jamie swallowed. "I think it's getting ready to-" he began, but before he could even say charge, it did.

The Kelpie seemed to grown in size as it bore down on them, head down, hooves churning the river.

When the Kelpie was almost upon them, Jamie felt Niamh's arms around him and just had time to hold his breath before the two of them crashed into the surface of the river and everything turned to liquid.

#

The Doctor opened the TARDIS doors and took in the view. All around him were low hills, enclosing a pebbled shoreline some distance from the TARDIS, which stood in the shallows of a loch that lapped against the shore before rolling back and in through the TARDIS's open doors. The Doctor's attention, however, was caught by a man, standing on the shore. He was broad-shouldered, bearded, wearing a kilt and shirt with a woollen jerkin. In one hand he held something thin and glittering which caught and reflected the low evening sunlight, and in the other a long, heavy sword. He stared out at the Doctor with a resolutely squared jaw. The Doctor was about to raise a hand in greeting when he noticed the water filling his shoes.

"Oh! Oh, dear me," he exclaimed, skipping quickly out of the puddle and back into the TARDIS, closing the doors behind him.

In a room off the TARDIS control room, he rummaged through several chests and boxes full of various articles of clothing, before triumphantly pulling out a pair of Wellington boots. He returned to the control room and, as he sat in a chair to pull them on, he noticed a light flashing on the console. "That's odd," he said. "That's only for concentrated, high energy readings. There shouldn't be anything like that here."

Once he had finished putting on the boots, however, the light had dimmed again, so he ignored it with a shrug and made his way to the doors, stepping out and splashing his boots into the water. "Ah, there now, much better." He smiled, rubbed his hands together, and began wading to the shore.

"Hello!" he called out to the man when he was within earshot, but there was no reply. When the Doctor was close enough, he saw the man was missing several fingers on the hand which was holding what appeared to be a horse's bridle made from a silvery, shimmering material. His other hand tightened its grip around the hilt of the sword.

"How do you do? I'm the Doctor," he said, trying to lessen the tension.

The man looked him up and down and then grunted, unimpressed. "I might have known the Devil would send an Englishman to finish the job."

"English? Oh, no, but I do get that rather a lot," replied the Doctor. "And as for finishing jobs for the Devil?" he added, trying to keep his tone light, "I don't get that quite as much, I'm pleased to say. No, you see, I'm actually looking for a young friend of mine. A little taller than you, wearing a similar sort of kilt, rather long-ish brown hair? Oh, I never was very good at describing him - it's got me into trouble in the past, you know."

"I saw you come out of yonder box," said the man. "Appeared out of nowhere, it did."

"Yes... yes, it does that," said the Doctor, carefully. "There's nothing magical or supernatural about it, though, I assure you."

There was an uncomfortable silence as the two regarded each other. The Doctor gave a weak smile and the man grunted again, before looking away, out over the loch.

"I've seen no one but yourself," he said, with a tone of finality which suggested he considered the conversation over.

The Doctor was about to say something else regardless, when there was a huge splash from the loch behind him. He turned to see two columns of water rise straight up out of the loch, hang for a second in the air, and then fall back down with an even louder splash, revealing two figures.

The Doctor was already running towards them as best he could, wading through the waves in his wellies.

Out in the water, Jamie straightened up and let out the breath he'd been holding. "Aw, ye've gone and soaked me again! I'll never dry off at this rate-"

He broke off when he saw Niamh wasn't moving but lying curled on her side, her clothes, tugged by the tide, looking more like tangled river fronds than ever.

"Jamie!" the Doctor cried. "Thank goodness it's you! What happened?"

"Doctor!" Jamie said, too concerned about Niamh to be shocked at meeting his friend like this. "We've got to help her! I think it's the travelling - the way she goes through the water. It's nae good for her."

The Doctor bent down to Niamh. "Well, she has travelled an incredibly long way. Haven't you, my dear? Come on, Jamie, help me to get her up."

Together, they lifted Niamh to her feet and half-carried her towards the shore.

"Och, she's hardly breathing, Doctor!"

"I know," replied the Doctor. "Excuse me!" he called to the man on the shore. "Can you help? Our friend here is in rather a bad way."

The man glared at them for a moment, and Jamie was afraid he would refuse, but then his face softened just a little. "Come on," he said, gruffly. "You can take her on up to the farmhouse."

#

The farm stood at the top of a low hill overlooking the loch and together they carried Niamh up the coarse dirt path leading to it.

"I do beg your pardon," said the Doctor, "I'm afraid I didn't catch your name."

"Douglas McKinnon," was the only reply from the man, as he pushed open the door to his home.

"Pleased to meet you, Mr McKinnon. As I said, I am the Doctor, and this young man is my very good friend, Jamie McCrimmon. And Jamie, your friend is?"

"Her name's Niamh," said Jamie, hurriedly. "But, Doctor, come on, we've got to do something! She's fading away."

"Yes, we'll do all we can, Jamie, don't worry."

Together, they carried Niamh to the single chair in the farmhouse kitchen and sat her down. Her head lolled forward as if there was no strength left in her body. The Doctor dug his hand into one of his pockets, then another, and finally pulled out a slim torch. Gently, he lifted Niamh's head and shone the light from the torch into her eyes. Behind him, McKinnon gave a grunt of surprise at the sudden light, but said nothing.

"If only we knew what she was," said the Doctor, "I might be able to help her. I mean, she's clearly not human."

"Not human!" McKinnon scoffed, but the Doctor ignored him.

"She said she's a Glaistig, Doctor."

"A Glaistig, eh?" said the Doctor. "I've heard of them, but never actually met one before. Now, what do I know about - oh!" He straighted up sharply. "Mr McKinnon, do you have a bath tub? I need you to fill it up immediately!"

McKinnon glowered. "I'd have to put the water on, and I've no got a fire going."

"Cold water is fine, man!" snapped the Doctor. "Just hurry! It's our only chance!"

Despite himself, McKinnon hurried from the room and soon returned dragging a large wooden bath tub. "You - Jamie, was it?" he said. "Come with me. There's a well outside but we'll fill it quicker with two carrying the buckets."

As they rushed out, the Doctor lifted Niamh from the chair and carefully laid her in the tub. She sighed in his ear and her hand slipped from his shoulder.

"Come now, my dear," said the Doctor. "Hold on for just a little while longer and I'm sure all will be well."

Soon, Jamie pushed his way back inside carrying a slopping bucket of water. He poured it into the tub, watched as the water filled to a pitiful inch high, then dashed out again. Niamh groaned and writhed in the shallow water, as though trying to bring it in contact with as much of her skin as she could. Moments later, McKinnon came in and emptied his bucket, and so it went on until the tub was nearly full to overflowing. Niamh slipped beneath the water and was still.

"Doctor," said Jamie, "is she...?"

The Doctor peered at her for a moment, then stepped back with a sigh of relief. "I think she's going to be all right."

"Right. Are either of you gonnae tell me what's going on?" grumbled McKinnon, sitting down in the chair and folding his arms.

"Well, Niamh is a Glaistig, Mr McKinnon," said the Doctor. "A water spirit."

"I ken what a Glaistig is," McKinnon said, "and I say there's no such creature."

"Come now, you don't really believe that. Otherwise, why would you fill the bath for her? Why aren't you concerned that the young lady hasn't come up for air? Anyway, you'll see in a moment. The water will restore her." The Doctor broke into a delighted smile as Niamh lifted her face out of the water, her eyes still closed, and took a slow, strong breath. "And so it has!"

"Hey, wait," exclaimed Jamie, "did you say McKinnon? Niamh said she was the guardian spirit for a McKinnon family and their farm. Is that you, do you think?"

McKinnon scowled and shook his head. "It's just me here now, and my family has had no guardian spirit, believe me," he said.

Niamh sat up in the tub. "It's true," she said, although her voice was still weak. "When I was young I strayed too far from the water, from a foolish desire to see what lay across the land. I hadn't the strength to get back and I was close to death. Your great grandfather found me, helpless and alone, in one of his fields. I was so afraid but his only thought was to help me. I managed to explain and he carried me back down to the river. As my strength returned, I vowed to watch over his family from that day on."

As Niamh told her story, McKinnon hands tightened into fists until his knuckles whitened.

"Where were you then?" he said, his voice strained. "Where were you?"

The Doctor and Jamie exchanged puzzled glances but Niamh clearly knew what he was referring to. "I was there," she whispered.

"You were there? You were there, twenty years ago, when those Kelpies took my brothers?"

Niamh nodded mutely.

"Some guardian you are," he said, choking back a bitter laugh. "They nearly took me too, did you see that as well? Lord help me, I even wanted to go with them. But as I touched the Kelpie's watery skin, I saw the others ride off with my brothers on their backs. They rode straight into the loch and under the water and were drowned. I panicked, tried to pull away, but the skin of the Kelpie gripped me and wouldnae let go." He lifted his scarred hand, missing all but its index finger and thumb, and held it in front of Niamh's face. "I had to use my dirk to cut off my own fingers, just to escape."

"They're not of the land!" cried Niamh. "I tried to stop them, I did! But these things you call Kelpies, they put invisible walls around water, walls that sizzle and bind, walls that I cannot breach."

McKinnon let his mutilated hand drop. "Well, I didn't need you then, and I don't need you now." He lifted the silvery bridle from the kitchen table. "I saw one of those blighted Kelpies down by the loch and I took my sword to its throat before it could work its foul magic upon me. I only managed to cut this bridle from it, but it drove the thing mad. Sent it thrashing and stamping back into the water from which it came. And if I can hurt them, maybe that means I can kill them."

"And that's what you were doing on the shore when I arrived?" said the Doctor. "Waiting for it to come back?"

"That's right," replied McKinnon. "I was looking to finish this, one way or the other."

"May I see the bridle?" asked the Doctor.

McKinnon shrugged and tossed it to him. The Doctor laid it on the table, took a penknife from his pocket and slit open the side, pulling back the fine metallic material and revealing a mesh of intricate circuitry inside.

"What is it, Doctor?" asked Jamie, peering over the Doctor's shoulder.

"I recognise the design," said the Doctor. "It's used by an alien race known as the Whidah. Terrible creatures, they built an empire by enslaving entire races, first on their own planet and then spreading out across the stars, forcing whole planets into servitude with the use of telepathic circuits and mind control."

"And they're here?" exclaimed Jamie. "On Earth?"

The Doctor thought for a moment. "If they were, I imagine we'd be in rather more immediate danger. So why - oh, of course!" The Doctor told Jamie about the scanner reading he had picked up in the TARDIS when he arrived. "It must have been a small scout ship which crash landed in the lake."

"Loch," said Jamie.

"Pardon? Oh, right, of course. Well, that explains these Kelpies."

"It does?"

"Oh, Jamie, do try to keep up! The Whidah have machines, of a sort, incredibly advanced, which combine forcefield technology with telepathic circuitry, and this," he pointed to the bridle, "is used to control the whole thing. It allows the Whidah to create slave-catchers out of whatever material is lying around - in this case, the water of the lake - sorry, loch - without having to carry around a lot of bulky machines. If they'd crashed in the Sahara, perhaps they'd appear as camels made out of sand. When not activated, one of these - well, we'll keep calling Kelpies, shall we? - could easily fit into your pocket."

McKinnon tutted and shook his head. "You're talking nothing but nonsense."

"Aye, he does that," said Jamie. "But he's no usually wrong about it, though."

"Yes, thank you, Jamie. The Kelpie constructs must have activated themselves when the spaceship crashed and they've been automatically scouring the surrounding area for slaves to repair the damage."

"But the ship's at the bottom of the loch!" said Jamie. "Anyone taken down there is just gonnae drown, not help with any repairs."

"That's computers for you," said the Doctor. "With no one left alive to program them properly, they're simply carrying out the basic set of commands built into them."

"Still sounds like nonsense tae me," said McKinnon. "What I want to know is how are we gonnae stop them? You do want to stop them, I take it?"

"Oh, very much so," said the Doctor, "and I think I know how. Whidah computers are fiddly little things, but simple enough to reprogram if you know how. Let me see now, where did I put my sonic screwdriver?"

While the Doctor tinkered with the bridle, Jamie checked Niamh was okay and then went to look out through the kitchen window, across the loch.

After a couple of minutes, he said, "Doctor? Are you about finished what you're doing there?"

"As a matter of fact, I am. I've rerouted the circuitry so that it should send a command to shut down all of the Kelpies."

"So it's ready to go?"

"Yes, Jamie, it's ready to go."

Jamie pointed out of the window, down towards the loch. "Good," he said, "because so are the Kelpies."

#

The Doctor hurried to the window. Although the sun had all but set, he could see the water of the loch churning and spotted the shapes of massive horses, picked out in moonlight and a pale blue glow all of their own. One by one, the Kelpies rose from the water and made their way across the shore, heading for the path to the farmhouse.

Jamie gasped. "There must be about a dozen of them!"

"Not to worry, Jamie," said the Doctor. "As soon as they come within range of this bridle, they'll be no problem at all."

"What is the range of that thing?"

"Well, I'm not sure." The Doctor held it up and peered at it nervously. "To be honest, I thought it would have done something by now. Perhaps if I take it outside."

Jamie reached for the bridle. "Let me, Doctor."

"No, no - I might need to make adjustments to the programming."

"Well I'm coming with you."

McKinnon lifted his sword. "And me. They'll no trample my farm without a fight!"

"I will fight alongside you, to protect McKinnon Farm." Niamh started to stand but the Doctor rushed over to her.

"Ah, no, I think it might be best if you stay here," he said, as she started to protest. "You need to recover your strength and everything we do out there is going to be on dry land."

Niamh stood up and said, "I have enough strength to fight."

The Doctor looked in her eyes and saw that she was lying, but he also saw something else there, a defiance that he recognised and had to respect. He nodded, and took her hand as she stepped from the bath.

The four made their way outside, McKinnon going first, brandishing his sword and Jamie right behind him, clutching his dagger. At the far end of the farmyard, the Kelpies were coming into sight, some rearing up and flailing their front hooves, others with their heads down and pawing at the dirt.

"Oh my," said the Doctor, who was seeing them for the first time. "They really take the angry horse bit seriously, don't they?"

He checked the bridle again as the Kelpies galloped up and quickly surrounded them. "Why isn't this working?" he muttered to himself.

"Come on!" yelled McKinnon at the Kelpies, turning on the spot and holding his sword out in front of him. "Come on!"

Without saying a word, Niamh pushed past the others and sprinted across the yard. Jamie called after her, but the Doctor held his arm. "I think she knows what she's doing," he said, but the last they saw of her was when she stumbled before disappearing behind the throng of furious Kelpies.

"At least, I hope she does," said the Doctor.

One of the Kelpies charged towards them, and McKinnon swung his sword, the blade glancing off the side of the Kelpie's neck. McKinnon only just managed to step aside in time before being trampled.

As the Kelpie passed, the Doctor something which looked like a glowing blue lozenge, floating in the centre of the Kelpie's watery body.

"That's it!" he cried. "Of course! The bridle is just the control mechanism. It's the main forcefield generator which governs communications between them."

"What are ye havering aboot?" shouted McKinnon, taking another fruitless swing at an attacking Kelpie.

"Somehow, we need to get this bridle back onto the Kelpie you attacked earlier."

"Finally, something I can understand," Jamie said, snatching the bridle from the Doctor's hands and racing towards the Kelpies.

"Jamie, no!" the Doctor shouted after him, but it was no good.

Jamie ducked under hooves and dodged the attacking Kelpies until he spotted the one which did not wear a silvery control bridle. With a defiant cry of "Creag an tuire!" he threw himself at it, his hand grabbing at what would have been the mane of a natural horse. Instead, he felt a buzzing crackle and realised his hand was stuck fast, as though fused with the body of the Kelpie. It reared up, pulling him off his feet. Even without the control bridle, the Kelpie relied on its default programming, and now that it had touched a potential slave worker that programming was commanding it to return to the ship. Making an effort not to touch it with the hand which held the bridle, Jamie swung himself up onto the construct's back, as the Kelpie thundered back down the path towards the loch. Almost his whole body now felt the unbreakable grip of the forcefield. The Doctor's calls receded behind him as Jamie was carried away.

"Hold still, you filthy beastie!" he yelled, as he tried with his one free hand to throw the bridle around the Kelpie.

Ahead, the loch loomed deep and dark and deadly, and in seconds the Kelpies hooves were splashing through the shallows.

"Aw, no," said Jamie, realising he had run out of time.

As they were about to enter the water, a massive column of water shot up from the loch in front of them causing the Kelpie to rear back on its hind legs.

Jamie seized his opportunity and quickly looped the bridle over the Kelpie's head, which promptly dissolved leaving Jamie sitting on nothing but gallons of falling water. He hit the surface of the lake with an almighty splash.

As he struggled to find the surface, he felt hands under his arms, pulling him upwards. When he had got his head above water, he saw that it was Niamh.

"How?" was all Jamie was able to say.

She smiled as she helped him back to shallower water. "The well in the yard. When the water is connected it is all one to me."

"You jumped down the well? Fair play to ye, lassie, that was some quick thinking, and brave too."

The Doctor and McKinnon were running down the path towards them.

"Jamie! You're all right!" shouted the Doctor.

"And you did it, lad," said McKinnon, his beard lifting in a smile for the first time since they'd met him. "All of those creatures disappeared at once."

"Och, no," said Jamie. "It's Niamh you should be thanking. If she hadn't stopped the Kelpie in its tracks I'd have been done for!"

McKinnon rubbed the back of his neck. "Aye, I see that now. Niamh, I'm sorry. I was too caught up in my grief to see that you were trying to help all along. You saved my farm, and this daft auld man with it."

"There is no need to apologise," said Niamh, shyly.

"Hey now," said Jamie, a thought occurring to him. "If the two of you got married you could keep the farm going together! Don't you think they'd make a bonnie couple, Doctor?"

"Now, Jamie," admonished the Doctor. "I'm not sure that's entirely appropriate."

"No," said McKinnon, firmly. "I'd no take a wife who's bound to me by an oath made before I was even born." He looked up at the farmhouse on the hill. "In fact, if I can, I'd like to release you from that oath. I think that would be best. Yes, go and live, Niamh the Glaistig. Go, with my thanks."

Niamh waded towards him. "And so my oath is done," she said, "and I am free to make my own decisions, to go where I will, to live as I choose." She kissed him on the cheek. "So perhaps one day I may swear another oath, and you to me? In time."

After a moment, the Doctor cleared his throat. "Gosh, well, we really should be going. It's been lovely meeting you both. Come along, Jamie, never mind gawping."

The Doctor stopped and turned back. "There is one thing that puzzled me," he said to Niamh. "How do you manage to travel through time?"

Niamh frowned. "Time?" she asked, as though the word held no meaning. "I simply go where the river takes me. Sometimes the river is very, very long."

The Doctor nodded and smiled. "That it is," he said. "Well, goodbye."

Niamh turned to Jamie. "The river sang true, Jamie McCrimmon," she said, and hugged him. "I hope it sings to me of your deeds again one day."

Jamie began to stutter a bashful farewell and was relieved when the Doctor took his arm and led him away, waving a last goodbye.

"What did you mean, travel through time?" Jamie asked, as they waded back to the TARDIS.

"I don't suppose it matters much now," replied the Doctor.

From the shore, Niamh and McKinnon watched as the two went inside their strange blue box. Before the doors closed, they caught Jamie's voice on the wind.

"1792?!"