Elsa was in agony, and in more ways than one. It started with her feet complaining at having to run once again in inappropriate footwear, so shortly after a strenuous trek that the lower gravity had failed to make much easier. Next was her whole body reminding her that morning was a very long time away for her, a time that had been occupied by a lot of running, getting nearly erased from existence, using her powers so intensively she had fainted, and far too little rest. But all that was a mere inconvenience compared to having no idea where her sister was and whether she was all right or not. As she did her best to keep up with the Doctor and Kristoff, Elsa tried to spare as much attention as she could to the shadows around them in case they turned out to contain Anna. She hoped she had correctly understood that her sister had proposed to meet outside, as the Doctor had told them - but since that was also where they were supposed to be going, shouldn't they have met by now? Elsa did not doubt her sister's resourcefulness, but she knew that orientation was not one of Anna's strong points, and that the dark, alien structure they were in did not help. She had little idea of the way to go herself and could only hope that the Doctor was leading them there. At least, Anna did not have a Dalek on her tail like they did…

"Wait!" Elsa said, slowing down, which was very welcome to her feet. "Is the Dalek still following us?" She tried to catch the periodic shrieking of the creature tailing them, and realised it sounded very distant where she next heard it.

"What are you doing, Platinum?" the Doctor asked. "Giving it time to catch us?"

"No, but… what if it went after Anna, instead?" Elsa said, slowing further down.

"Look, I don't know if you got this," the Doctor said, doubling back to her, "but this is the part where we run to avoid getting exterminated. Freckles can run too, right?"

"Yes, but… if we are heading toward the exit and we don't see her…"

"Then she will find another exit or a good hiding place. Listen, Platinum, I know this is hard for you, but you will have to trust your sister to be able to… Run!" the Doctor shouted suddenly, looking past Elsa.

Elsa glanced behind her and gasped. A small group of Ice Warriors had emerged from a branching corridor, heading purposefully toward them, the glow from the sticks in their foreheads making small blue waving dots. Elsa felt Kristoff's hand closing on her wrist and pulling her forward.

The mad dash resumed across the strange rooms. Elsa had to admit that Anna had been right when she had told her she needed more exercise. She had done her best in the past year to catch up with the time she had spent locked in her room, but that had apparently not been enough to prepare her for the kind of exercise that seemed to be common when accompanying the Doctor. What helped her though, apart from the occasional pull from Kristoff or the Doctor, was the terror she felt at their pursuers - a terror, she was ashamed to realise, that was mingled deep-down with a seething hatred. The fact that for now she could do nothing against these Daleks and what they had made of these poor Ice Warriors only reinforced it.

Elsa was now completely lost. The Doctor seemed to be taking turns at random, and she hoped against reason that one of these turns could still put them in Anna's path. True, if her sister was followed by the Dalek it would not be an improvement for either of them, but at least Elsa could stop worrying about her sister's fate.

She was running a bit behind the Doctor and Kristoff when she noticed a light in front of them, and Kristoff let out a cheer. It took her a few seconds to realise that the light was coming from the Martian sky through an opening in front of them. Looking around, she thought she recognised the room where they had first arrived.

There was another shout from the two men. To her horror, Elsa saw two Ice Warriors surging on either side of the hole, their arms raised toward them. Behind her, she heard the already familiar shrieking of a Dalek getting closer accompanied by the stomping of more pursuers.

The Doctor skidded aside and vaulted over a debris. Kristoff managed to follow him, flailing desperately to catch Elsa's hand and failing. He called her name as he jumped behind the Doctor, just as one of the Ice Warriors fired his weapon. It emitted a high-pitched whistle, and a device close to Kristoff exploded in a shower of sparks.

Elsa realised that the Doctor and Kristoff had managed to dive into a branching corridor. Both of them shouted, but she did not understand what they said above the pounding of her heart. It was too late for her to turn now. Carried by her momentum, she had already passed the corridor's entrance and was closing in on the Ice Warriors. There was no place to take cover on either side of her now, and stopping was not an option. The closest Ice Warriors were only a few yards away, and already pointing their weapons at her.

The thought that maybe Anna would be waiting for her outside gave Elsa a last rush of energy and insight. She accelerated toward the Ice Warriors facing her, bending as low as she could. She sidestepped as one fired his weapon, crouched under a claw that was attempting to grab her, and squeezed between the two Ice Warriors as they flailed slowly in their attempts to catch her. There was the whistle of a weapon behind her, followed by an uncomfortably close bang on the wall nearby.

And then she found herself running along the shaft through which they had entered, with the circle of blue sky in front of her growing closer. She let out a little cry of triumph and tried to coerce her straining legs into accelerating even further.

Elsa remembered too late that gravity played a strange trick here, as she felt the floor tilt up under her, as if trying to throw her backward. But the sudden change was not enough to stop her. Scrambling madly over the metal floor as it became a wall, she managed to resist the pull long enough to throw herself out of the Dalek ship. Almost blinded by the light from the sun, her head spinning because of the sudden change of gravity, she landed haphazardly a few feet from the opening. She gathered her wits as she heard a scraping inside the shaft – which had been a narrow corridor a second ago - and half ran, half fell away from the hole on the curving surface of the Dalek ship.

She jumped after a few yards, and rose in an impossibly long arc away from the buried ship, landing on the edge of the crater in which it was buried. As she scrambled away, she heard a distant whine, and rocks near her exploded as if struck by something invisible. Without taking the time to get her bearings, Elsa ran away from the ship as fast as she could, diving into the first crevice she found to get out of sight.

She called Anna's name, just in case her sister had managed to leave the ship with less pursuers and was waiting for her nearby, then as no answer came she set off running madly through the rocky landscape, trying to get away as fast as possible from the Daleks and their servants.

Kristoff did his best to follow the Doctor as they ran through the vast rooms and corridors of the ship. He was sure he could have overtaken him if he had tried, even with the surprising turn of speed the older man displayed, but, unlike him, the Doctor was able to navigate the strange place as if he was familiar with it. He was also constantly changing directions, turning into side corridors Kristoff would never have noticed as they passed them by, jumping behind any large debris he could find, and Kristoff preferred to stick with him rather than find himself lost inside this strange place. Another reason why he tended to lose ground to the Doctor was that he kept looking behind him to see if by any chance Anna or Elsa would have caught up with them. But, ever since they had branched into this separate tunnel away from Elsa, only the stomping of the Ice Warriors and the shrieking of the Daleks could be heard behind them.

Eventually the Doctor slowed down as he entered a smaller room, and swiftly crouched behind some large debris that occupied half of it, signalling Kristoff to follow him. They both remained crouching there while their closest pursuers crossed the room, completely missing them. Kristoff got ready to rise to his feet as soon as they had left, but the Doctor motioned him down. A while later, another group of Ice Warriors stomped across the room, followed by a Dalek who could be heard shrieking some time before it arrived. After some more time which felt like ages to Kristoff but was probably closer to 5 minutes, the Doctor slowly unfolded.

"Now they'll be searching the next quadrant of the ship. Come on, Reindeer Man, let's go."

"Are we going after Anna and Elsa yet?"

The Doctor paused, as if considering the idea required him to think hard.

"No," he said at least. "Why would we?"

"What? Because they may have been captured by those… those things!"

"So you think it'd be a good idea if we were captured too?"

"Sorry?"

The Doctor sighed, as if the discussion was exhausting him.

"Listen, Reindeer Man, either Platinum and Freckles have been captured and are now surrounded by Daleks and their puppets, or they found a safe place to hide inside the ship, or they have managed to escape it. Either way, we can't do anything about them right now."

"But… but what if they were captured, and the Daleks are trying to kill them?"

"Oh, the Daleks don't need to try to kill people, they are good enough at it," the Doctor said off-handedly. "But I don't think they would kill them right away, though. The Daleks are many things, but they are not stupid. They will notice they are not Ice Warriors, even if the difference is subtle. They will probably try to interrogate them first to know why they're here."

"And what will they do after that? Will they… Anna said you told her they could… turn people into them?"

"Oh, yes, good point, Reindeer Man. Yes, they could certainly try to do that. Why waste bodies after all."

Kristoff reached and grabbed the Doctor by the lapels of his coat. He did not slam him into a wall, mostly because the nearest wall was torn and full of jagged edges, but lifted him by a couple of inches.

"Now, listen to me, Doctor whoever!" he hissed, trying to keep his voice low despite his anger. "I love Anna, and I care about Elsa. I won't let either of them be killed or turned into those… things, without doing anything! So I don't care what you want to do, I'm going to go after them!"

"And what will you do if you find them?" the Doctor said calmly, as if being suspended by his lapels was a perfectly normal position for him.

"I'll try to save them of course!"

"And if you get killed for your efforts?"

"Then at least I'll have tried!"

"OK. Suit yourself." The Doctor's tone was so calm that Kristoff let go of him out of surprise.

"What?"

"Go do whatever you want to do to save your girlfriend and her sister, if you want to do it so much. I won't stop you."

"But you… what are you going to do?"

"What we came here to do in the first place. Find out whatever the Daleks are doing here, apart from heating up the atmosphere and converting Ice Warriors into puppets, and stop it all."

"And how are you going to do that?"

"Haven't got the foggiest. But a good starting point would be finding their main control centres. I think I have a better idea of how this ship is organised now, so they should be easy to find. I'll be going there now, and I should have a plan by the time I arrive. Oh, and by the way," the Doctor added as an afterthought, "that's also probably where your girlfriends will be if they took them prisoners. I'll tell them you were looking for them if I see them there. Toodle-oo!"

The Doctor vaguely waved his hand in something that might have been a salute, and strode off.

"Hey!" Kristoff called after a second.

"Oh, you'd prefer to call the Daleks here to be killed right away. That's very efficient. Just let me move away before they arrive."

"Were you being serious? About Anna and Elsa being where you're going," Kristoff said, catching up with him.

"It's a possibility," the Doctor said, shrugging. "Probably your best chance of seeing them again if they have been captured."

"And if they've not?"

"Well then they're either outside or well hidden somewhere, and your best chance is to either leave this ship to scour the surface of Mars or stay inside to search it ."

With that the Doctor turned and moved away purposefully. Kristoff let out an exasperated groan and went after him.

Years ago, while she was playing on her own in the castle, Anna had managed to entangle herself into an old suit of armour. After a while she had realised that, no matter how much she struggled, the armour would not budge one inch, as if it was made of stone instead of old metal, and she had only been freed when servants had heard her cries. Struggling against the grip of the Ice Warrior who had caught her reminded her of this incident, and she had eventually ceased trying to break free, letting her captors half-carry, half-lead her through the alien ship. She had refrained from shouting for help though – she was not sure how many Ice Warriors were around her now, but in any case she did not want to cause anyone to be captured trying to rescue her. She could only hope Elsa, Kristoff and the Doctor had managed to escape on their own, and took some hope in the fact that the Ice Warriors had not killed her on the spot. Maybe she would be able to talk her way out of this.

Eventually they reached another large room, where some Daleks were gathered around strange apparatuses. Her captor walked up to one of them and stood to attention, holding Anna by the shoulders in front of him. The Dalek slowly turned its head so that its glowing stick faced her, and Anna noticed that the bulbous end also seemed to contain some sort of eye, which seemed even more alien than the one from the Ice Warrior's.

"REPORT!" the Dalek intoned.

"This intruder was captured," the Ice Warrior holding her said in a flat, emotionless tone. It did not even have that heavy breathing Anna had come to associate with Ice Warriors.

The eye-stick moved up and down as if it was examining Anna from head to foot.

"YOU ARE NOT NATIVE TO THIS PLANET," it shrieked. "HOW DID YOU ARRIVE HERE? EXPLAIN!"

"Wait, what? Oh, er, yes, I'm, I'm from, uh, Earth. That's, uh, that's another planet. You could probably see it in the sky, it looks a bit like a star but it does not twinkle, I wonder how it would look from here…"

"NO POWER IN THIS SYSTEM HAS ACHIEVED SPACE TRAVEL YET. HOW DID YOU GET HERE? YOU WILL EXPLAIN!"

"Well, I came with… uh."

Anna hesitated mid-sentence. She had hoped to be able to make Daleks listen to reason if she showed herself open and truthful. Yet at the same time she remembered the Doctor saying he had been fighting them for some time, and the Dalek they had met in the base shouting something about him. Maybe admitting an association with their enemy was not the best way to make the Daleks listen to her.

"ARE YOU ONE OF THE TRAVELLING COMPANIONS OF THE DOCTOR?"

"Well, er, yes, I, uh, came with him here, but, listen, did you ever try talking to him? Because he's actually nicer than he appears and…"

"WHERE IS THE DOCTOR? YOU WILL TELL US!"

"But I don't know where he is now! We got separated!" Anna said, relieved at the idea that the Daleks did not seem to have caught the Doctor, which probably meant that Kristoff and Elsa were free as well.

"YOU WILL TELL US! YOU WILL TELL US!" the Dalek shrieked, becoming shriller with each syllable. "YOU WILL TELL US OR YOU WILL BE EXTERMINATED!"

"But I DON'T KNOW!" Anna shouted back. "And I don't think I'd tell you if I did! Why do you want to know where the Doctor is anyway?"

"THE DOCTOR IS AN ENEMY OF THE DALEKS! THE DOCTOR MUST BE LOCATED AND EXTERMINATED! WHERE IS THE DOCTOR?"

"I already told you that I don't know! And, seriously, why do you think the Doctor is an enemy?"

"THE DOCTOR IS THE PREDATOR OF THE DALEKS! THE DOCTOR MUST BE EXTERMINATED BEFORE HE CAN INTERFERE! THE DALEKS SHALL PREVAIL!"

"OK, but the Doctor said you are the evil ones, so maybe this is all a misunderstanding – well, er, apart from your turning those nice Ice Warriors into puppets things, but maybe this can be fixed. What if you took the time to explain what you want, and then maybe we could reach an agreement…"

"DALEKS DO NOT REACH AGREEMENTS! DALEKS ARE THE SUPERIOR LIFEFORMS! ALL INFERIOR LIFE FORMS MUST BE EXTERMINATED!"

Another Dalek glided next to the one Anna had been talking to.

"THERE IS NO NEED FOR FURTHER INTERROGATION," it intoned. "WE HAVE SECURED THE DOCTOR'S SHIP. WE WILL AMBUSH HIM IF HE TRIES TO RECOVER IT."

"I UNDERSTAND," the first Dalek said, turning its head toward the newcomer. "THE CAPTIVE WILL BE EXTERMINATED AND CONVERTED."

"Wait, what? No, you don't want to exterminate me right now! I'm… I'm sure there are a lot of things we could talk about! What… what do you want, for instance? Maybe I could give it to you right now and you would not need to kill anybody else, especially not me! Just talk to me! People feel better when they talk!"

The second Dalek turned toward her and slowly glided until it was a foot away from her. Its eye-stick twitched a few times as if it was inspecting her.

"WE WANT THE TOTAL EXTERMINATION OF ALL INFERIOR LIFEFORMS IN THE UNIVERSE. THE DALEKS EMPIRE WILL PREVAIL!"

"Wow, that's a bit, uh, harsh. Not for your empire prevailing, I mean, we also have empires back home who tried to expand but… what are inferior life forms exactly?"

"ALL LIFEFORMS THAT ARE NOT DALEKS!"

"EXTERMINATE THE HUMAN!" the first Dalek shrieked.

"No, wait! I can… I can… I mean… I'm sorry that I'm inferior, but if I hide far away then you won't have to bother about me and…"

"EXTERMINATION IS UNNECESSARY," the second Dalek intoned. "TAKE THE HUMAN DIRECTLY TO THE CONVERSION CHAMBER!"

"I obey," the Ice Warrior holding her said in his flat tone.

"Wait, what? What is a conversion chamber? What are you going to do to me?"

But the Ice Warrior had already begun turning around and, ignoring Anna's futile attempts to free herself from his grip, marched out of the room, followed by the squad of Ice Warriors.

Elsa cautiously raised her head above the rocky ridge and tried to get a look at the surroundings of the Dalek ship – which appeared once again as a hill now that she was far away from it. She had tried calling Anna, Kristoff and the Doctor, but had gotten no answer – and had tried to avoid raising her voice too much in any case. She preferred risking missing Anna than drawing the attention of the Daleks, especially if her sister had managed to hide successfully.

She started as she saw a movement on the hill. Looking up, she saw a Dalek apparently emerging from the ground, which flickered briefly around it. The thing was flying slowly, turning its head left and right, the stick protruding from it directed at the floor. At the same time, she saw some Ice Warriors appear near the base of the hill and spread outward, advancing slowly. And then the shrieking of the Dalek reached her, made weak by the distance but still understandable enough. The thing was repeating "search, locate, exterminate" in its metallic voice, over and over.

Elsa did not wait. She half slid, half ran down the slope back into the canyon where she had been hiding, and ran away as fast as she could, trying to stick to the bottom of canyons and heading anywhere as long as it seemed to be away from the fake hill.

Kristoff tried to flatten himself against the wall as he followed the Doctor through the corridor. Whatever he could think of the man, he had to admit he was far better at stealth than him – which was on the whole not very surprising since Kristoff had never been overly concerned with stealth, apart from when trying to avoid triggering an avalanche or, more recently, to surprise Anna. The grey-haired man was also apparently better at orienting himself, or at least appearing to do so, which was not a surprise either since Kristoff had little experience with navigating alien ships. However he was definitely suspecting that they had been going deeper into the ship, and were getting closer to where they had first begun to be chased. Even if the Doctor had told him this was the plan, Kristoff could not help getting nervous.

Eventually the Doctor stopped at the threshold of another room and poked his head at the corner to examine it. Kristoff waited patiently until he drew back and sat with his back to the wall.

"Interesting," the Doctor commented. "There is a geothermal converter that seems to be in working shape. When it's coupled with thermal expanders, it can be used to raise the temperature over an area, but not to the extent we have witnessed. It would need a much higher geothermal activity than what we have now."

"Er, what?"

"Oh, you're still there, Reindeer Man?" the Doctor said, looking at him as if he had just noticed the tall blond man standing next to him. "Forgot about you."

"If you've forgotten about me, who were you talking to?"

"Myself, of course. The only person here able to understand me."

"I think I know you, Doctor," Kristoff said after a while.

"Oh, really? So you could tell me who I am, I have been wondering."

"I've met people like you. Especially in the cities. The kind of people who think that they are oh so clever because they have studied books and want to make fun of the big stupid guy from out of town by using long words and thinking he won't understand them."

"I'm sorry, which one of those am I supposed to be again?"

"What?" Kristoff said, briefly thrown off tracks. "Well," he went on, rallying, "who are you, exactly? And why do Anna, and Elsa, like you so much?"

"I'm the Doctor. I'm a Time Lord from Gallifrey, and I'm 2000 years old. And I had once made a list of the reasons why people would like me. There was my dress sense, and the way I play the guitar, for starters, but we don't have the time to go through all of it now. Now, was that all you wanted to know?"

"OK, I get it, you prefer to make fun of me instead of answering a simple question. Now listen, I will try to remain polite because Anna seems to like you. You like to boss and belittle people around just because you know things that they don't, and I'm fed up with that. I'm fed up with you acting as if you were so much more clever than everyone else. So maybe you know your way around here because you are used to places like that, and you probably know a lot of things because you went to some fancy school like city people do. But I'm pretty sure there are things I know that you don't, Doctor. Like how to survive spending the night in a mountain while it's freezing and snowing. Or how to cut the ice without falling in the water. Or how to take care of a reindeer. So, yeah, all that is not very useful right now, but that's no reason to make fun of me. I wouldn't do the same to you if I was the one knowing my way around. Well, not much, I think. Not if you did not start by being rude to everyone around you, even Anna, who is always nice to everyone."

The Doctor examined Kristoff for a moment as if he had just met him.

"Do you know what a geothermal converter is?" he said at last.

"No. Er… no. Wait, you said geo… thermal, er, Anna told me once that, er, it had to do with… hot springs? Yeah, never mind."

"Actually, you are correct, as strange as it may seem. A geothermal converter is able to tap into underground geothermal energy, which can, indeed, cause hot springs. Its effectiveness depends of course on how geologically active the place where you are using it is, and what you're doing with it. If you connect it to thermal expanders, then you can use it to heat up the atmosphere. That's a common and cheap terraforming tool for geologically active planets. We are close to one of the largest volcanoes in your solar system, but it has been dormant for millions of years, so there should definitely not be enough geothermal activity left to increase the temperature so much over such a large area. Do you understand?"

"Er… no. Well… the Daleks are using… the heat of the volcano to, er, do something, maybe heat everything up, but the volcano is not hot enough?"

"Close enough," the Doctor said. "There is something I'm missing. But there are too many guards here. Let's move on, maybe we'll find a place with fewer of them around." The grey-haired man stood up and moved swiftly to another corridor. "Oh, and the first thing to do to survive in the mountains is not to go there when it's snowing," he said over his shoulder. "Barring that, you have to build an igloo if you don't find a shelter. As for reindeers, you just have to ask them what they need and listen to what they tell you. But you're right, it's been some time since I've done some ice cutting."

Kristoff followed the Doctor, his head spinning. The events of the day had been strange, but, until they had met the Daleks in the base, not that different from one of those days where Anna would insist on going on an adventure. Being raised by living rocks had made Kristoff rather broad-minded when it came to encountering strange creatures and magical places, and being Anna's boyfriend meant that you had to expect for a picnic to turn into an afternoon exploring a new cave or old ruins, and sometimes also a night trying to find their way back home after getting lost. But what had begun like a particularly strange afternoon had turned into a nightmare, during which they had been attacked by a merciless creature, Elsa had lost her powers, and Kristoff now was deep down into this unsettling place, separated from the love of his life, and accompanied by this abrasive man whom he could only hope to be able to rely on to get out of this situation, with the possibility of Anna or Elsa having been captured weighing heavily on his mind.

"Ah, here we are," the Doctor said after another trek through the metal corridors and rooms of the ship, during which they had needed to duck into dark corners a couple of times to avoid a passing Dalek or a couple of their eerie puppet Ice Warriors. "Keep watch, Reindeer Man."

The corridor they were in connected to another large room, but they were once again closer to its ceiling than its floor. The Doctor laid on his stomach and began to inspect the room below them. Kristoff crouched on the opposite side of the corridor, his back to him.

"Here it is," the Doctor said with some kind of grim satisfaction. Quickly glancing in his direction before resuming his vigil, Kristoff saw that the grey-haired man had whipped a pair of small binoculars from his pockets, of the kind Anna had told him was for attending opera and theatre.

"What is it?" Kristoff asked out of the corner of his mouth.

"Their conversion chamber. I hope it's the only one."

Kristoff poked his head over the ledge to get a glimpse of the room below. He registered a small group of immobile Ice Warriors, some more Ice Warriors lying on the ground, and a complex machinery into which three glass sarcophagi were affixed. There was also one Dalek near the large machine.

"That's where they turn the Ice Warriors into these… where they get this stick into their forehead?"

"Yes. They probably don't have enough nanogenes to do this on a larger scale, so they have to use these pods to convert them. Some good news, at least."

"Why? Because it's slower?"

"Well done, Reindeer Man. It will take them some time to convert these Ice Warriors corpses that their puppets probably brought back from the base. That will leave us some time to try… mmmh."

"What's wrong?" Kristoff said, resisting the urge to turn around to check what the Doctor had seen and concentrating on the shadows behind them. He may not have been able to understand what was bothering the Doctor just by looking anyway.

"You're not going to like this," the Doctor said, slowly crawling away from the mouth of the corridor. "They have just brought Freckles to one of the conversion pods."