As the spread fingers of the giant's great steel hand shot out at her face, Jasmine made one last frantic thrust at the pedals of her guardian's absurd electricity generating bicycle. At the same instant the Doctor plucked the light bulb from its setting, smashed it against the wall, and with cool precision touched the almost imperceptibly glowing element to the innards of the disc.

The monster froze. It's head jerked awkwardly to one side and the featureless circle of light at the front of its helmet flickered and went dark. It crashed to the floor like a toppled statue.

For a fraction of an instant a merry light sparkled in the Doctor's dull old eyes.

"There," he said. "Told you so."

Jasmine sagged forward over the handlebars, weak with relief and exhaustion, but the Doctor was instantly on the move. He made his way cautiously over to the felled machine and prodded its shoulder with his stick. A dull clank of metal on metal was the only response.

"Right. Jasmine, go and get a bucket of water."

"Wh... Whur?"

"Do it, please." He seemed to wilt before her eyes now that the crisis was over, suddenly very old and very tired, and his limbs trembled just from the effort of lowering himself into the nearest chair. "Your guardian isn't here," he said wearily once he was settled. "The other one must have taken him away. That means we still have a great deal to do tonight."

By the time Jasmine got back from the kitchen with the requested bucket he had revived a little, and from his slumped position had mustered the energy to start jabbing the metal man's head with his stick.

"Ah, good," he said, glancing at her. "Put it down and help me get the thing's head off."

She did as she was told and knelt on the rug, gingerly touching the cold metal sphere with her fingertips.

"Will it come off?" she asked. "It looks awfully sturdy."

"Normally it would be. It's magnetically locked. But now its power systems are down it should just twist off."

He'd been right about everything so far, she reflected, so she nerved herself to get a good grip on the head with both arms and started to drag it around clockwise. Meanwhile the Doctor leaned back in his chair, his eyes half closed, and began to talk quietly, calmly. Just as he'd lectured her many times before on pre-Renaissance sculpture or Polynesian history.

"I recognise these creatures. They're Klavites. They come from a planet whose surface is entirely covered by water, and as a result their whole technology and way of life has developed in the sea. They have gills, just like fish, and they see any excursion onto dry land as an exciting adventure. Unfortunately there's an unpleasant streak in their culture which holds that the best proof of such daring is to bring back specimens of the more dangerous wildlife. You understand that wildlife, from their perspective, includes you.

"That's what that little metal disc was for. It's bait, just like on a fishing rod. An animal is drawn to it, picks it up, and instinctively hangs onto it. Perhaps it gets attacked by a larger creature which wants to take it away. So by waiting for a day or two after the bait is first taken they ensure that when they put on their tin suits and venture out onto land it will be in the possession of the scariest of the local animals. That gives them the most impressive prize to take home."

Jasmine glanced up, as one fact crystallised amongst those swimming crazily in her mind.

"You're saying this is a costume? There's some sort of gigantic fish man inside?"

"Well, yes and no."

The head came free, and Jasmine fell back as its weight rolled onto her. There was a gush of liquid from inside, and along with it something tiny, blackish green and glistening tumbled onto the floor. Eight inches long, barbed, fish-like tail, tiny spindly arms like a starved baby, a slobbering, gulping mouth, and set deep into the sides of its head a pair of sharp yellow eyes, which as she stared at it in revulsion, stared spitefully right back at her.

Jasmine was startled by her own scream, but the Doctor's voice was still there.

"Put it in the bucket, Jasmine."

She reached out, but recoiled as the thing flipped about and scrabbled at the rug with its little hands.

"It can't hurt you," the Doctor said. "And it's suffocating now, just like a beached fish. Put it in the bucket before it dies."

Jasmine took a deep breath, and with a shudder, feeling the nausea welling up inside her, managed to get a grip on the Klavite's clammy body and with her eyes averted plopped it into the water. It instantly sank to the bottom, out of sight. She rubbed her hand dry on the rug.

"Now what?" she asked.

The Doctor closed his eyes for a moment in thought, and as the papery skin of his face became immobile it looked like that of something long dead, ready to crumble to dust at any second. But with a blink he was back again.

"Look at things from the Klavites' point of view. You've sent two men into a hostile environment and one of them hasn't returned. What do you do?"

"I... send someone to look for him?"

"Exactly. And they'll have been monitoring everything that happened from the ship, which means they won't fall for that trick with the pulse emitter and the bicycle a second time." The Doctor bowed his head and rubbed his hand across his eyes. "We... we have to move first. We should get down to the beach, to the place where you first found the disc."

Jasmine was silent, and he looked up at her with a weak twitch of a smile.

"I know, I know. I can barely get out of this chair." A wavering hand pulled his hat down over his eyes. "I'm sorry, Jasmine. I can't help you any more."

"Doctor!" She shuffled over to him, trying to peer under the brim of his hat as she took his hand. "Please, you have to. There's no one else."

"Yes there is," was the mumbled response. "He's coming now. I've called him and now it's time for me to step aside. Goodbye, Jasmine."

"What are you saying?" Distraught, she swallowed down the tears. "I don't understand."

"Sorry," his exhausted whisper was barely audible now. "So sorry. I wanted so much... To see the woman you'll become."

His voice fell away, and for a moment she thought he had fallen asleep. Then she felt something move under her fingers where she was holding his hand. Starting back, she watched in disbelief as the wrinkled, sagging flesh drew taut and smooth. The Doctor stirred, his head lifted, and visible beneath the brim of his hat was an unfamiliar jawline, a flash of white teeth, a curving, lopsided smile, and a pair of glittering ocean-blue eyes.