Despite his shocking outburst, Rose felt that Peter wasn't entirely to blame for his reaction or the situation it had left her and the Doctor in.

She should have known that it was all going to end badly.

They had been unwanted from the start and it had resulted in several clashes with the lieutenant even before they had reached the cave. Topped with the maddening chaos and stress of the constant attacks from the killer bats, it was enough to drive anyone mad.

What they had just discovered had simply been the trigger.

Yet it was all still somewhat unclear to Rose what exactly they had stumbled upon. Suspicion and speculation were all they had thus far in uncovering the secret Peter Argent was willing to defend at all costs.

But their attempt at getting him to come clean had been handled appallingly and it had utterly destroyed any chance of Peter and Stefan ever talking to them again.

Rose couldn't help but feel bad about her part in it.

"We shouldn't have said anything." She said. "It wasn't any of our business."

The Doctor hummed in agreement.

"Yes… But aren't you in the least bit curious, Rose?" He then asked her. "Mind you, I've already got a few possibilities in mind."

"No surprises there," Rose said with a smile. "But he doesn't look any different to you or me?"

"There are a lot of species that do." The Doctor countered. "Or you look like them. It's all a matter of perception."

"So what is he? Or what do you think he is at least?" She asked. "I mean.. He is an alien, right?"

"Oh most definitely." He replied. "One hundred percent not human."

There it was. It had finally been said.

Coming from the Doctor, Rose could accept it as completely true. The Time Lord was far too clever to get something like this wrong. She just wished that Peter had trusted them enough to tell them himself.

"He was so scared about us finding out. But why, Doctor? What kind of species is…?" She paused as a sudden thought occurred to her. "Is he dangerous?"

The Doctor regarded her with a serious look.

"I think he's probably about as lethal as anything we've faced tonight." He told her. "But he's on our side and I doubt he'll be trying to kill us anytime soon."

Rose laughed at this.

"You sure about that?"

The Doctor seemed to have entirely forgotten that less than five minutes ago Peter had been stood with a loaded gun pointed against his head.

"Fear can bring out the worst in anyone. But he and Stefan are still going to need our help, whether they want it or not."

"They told us to leave."

The way in which the Doctor smiled back at her told Rose that he had no intention of going anywhere else but onwards. Quite deliberately, the Time Lord planted his muddied Converse shoe one step further ahead of him.

"Oh, Rose." He told her. "Whatever makes you think that I'm going to do as I'm told?"

To her surprise, Rose was made to wait a further ten minutes before the Doctor led them on down the tunnel after the two soldiers. Explaining that it would be easier for the moment to tail them and jump in if and when the situation changed, Rose suspected that it just provided an excuse to avoid having another argument.

She had to agree with it, however.

If it came down bumping into one of the creatures or Peter and Stefan, it was hard to tell which would be the less dangerous option.

But despite the Doctor's revelation over the lieutenant's mysterious origins, Rose had still not seen any solid proof that he was indeed from another world. Overall, the idea of it being true had just risen more questions than answers.

"So Stefan is human, and he knows that Peter isn't?" She questioned as they walked. "So does that mean that Peter told him?"

"Perhaps he did." The Doctor replied. "They grew up together, and it would make sense that Stefan would know out of anyone. It must be hard keeping a secret like that to yourself."

"But no one else knows?"

"Well, I suspect that his adoptive parents must know. I doubt UNIT are aware. He wouldn't be working for them right now if they did."

"Why? They let you work for them." Rose reminded him. "Even brought you to Downing Street, didn't they?"

"I kind of started it all though. Seems only polite that I get an invitation now and then."

Eventually, they came to the end of the tunnel they had been travelling on and were suddenly confronted with a choice as it split off into two separate directions. One travelling to the left, and the other toward the right.

"Which way did they go?" Rose asked. "Mind you, they're going to be so mad when they see us again."

"We're here to help, Rose." The Doctor reminded her. "Still, seeing as we have no idea which way they've gone, we'll just have to guess."

From out of his coat pocket, the Doctor pulled out a very strange looking twelve-sided bronze coin that was no bigger than the tip of his thumb. "Heads to go left and tails to go right?"

"Sure…"

Unable to distinguish one side of the tiny coin from the other, Rose watched as the Time Lord flicked it up into the air and caught it swiftly again as it came back down. Flipping it onto the back of his hand, he revealed which direction it had decided to send them in.

"Tails. We're going right." He said. "Let's go."

Holding on tight to the leather sheath of the knife Stefan had given her, Rose cautiously followed after him.

In the limited light the torch was providing it was difficult to tell where the next step would take them. But almost immediately, she could tell that they were heading uphill as she felt the ground under her boots begin to steadily slope upwards.

To her immense relief, the horrid humid air also finally started to cool and become much more bearable to breathe in.

"Do you think we're close to the surface?" She wondered aloud. "Maybe there's another entrance nearby?"

"Maybe. But then again… Oh! Look at that."

It was the biggest part of the cave by far.

Much like the cavern they had entered from, there was a large pool of water making up most of the surface area. Curiously, unlike the blacked depths of its twin, this underground spring had an underlining glow as though someone was just underneath the surface shining a very faint light up towards them.

The result was a pale blue hue that rippled and danced across the roof that made it possible to see without using the torch.

But it was neither this nor the impressive size of the cave that had made the Doctor gasp with excitement.

Emerging out onto a pathway several meters above the ground, both he and Rose had the perfect vantage point to observe what inevitably had to have been found sooner rather than later.

The size of the spaceship was hard to judge given that more than half of it was missing.

Currently the size of a small house, it was the shape of a flattened egg. Propped up on three legs, the main entrance might have once had a ramp in order to access it. With it gone, however, a running jump looked to be in order should anyone wished to have ventured inside it.

Despite the air not being as humid here as the rest of the cave, the damp conditions had stripped away most of the hull's unusual black colour, making it instead bright red from rust and corrosion.

But overall the ship did not look damaged. It had not crash-landed here, and most of the missing components looked to have been removed purposefully. It was this that allowed the Doctor and Rose to glimpse into the heart of the ship's interior.

"They came here in that?" Rose guessed. "What happened to it?"

"They've cannibalised it." The Doctor theorised. "Taken it apart. Bit by bit."

"Why?"

"In order to survive." He said before pointing at it. "Look at the shape of it, though. That's a twenty-eighth-century design. You can tell by the colour, everyone has black ships then."

"They're from the future?" Rose asked. "Then how did they get here?"

"I don't know, but the real question is, Rose. How did they get into this cave? There isn't a hole in the roof."

Rose looked up at the intact ceiling.

It was impossible for anything, let alone a craft of this size, to have come through without creating a massive hole in the roof above. Hadn't Stefan said there hadn't been any reports of a crash? But then again, this spaceship had come from the future. Did that make it a time machine?

As far as Rose was aware, the only one in existence was the TARDIS.

"So how did it get here?" She asked. "I can't imagine those creatures flying it, can you?"

"There was always the possibility of them being smart, Rose." He told her. "Just to be sure though, a quick scan should tell us -"

The Doctor had fished out the sonic screwdriver as he had been talking and was already pointing the little metal tube in the direction of the ship when Rose suddenly caught hold of his arm.

"Wait!" She hissed. "Look."

On the ground, one of the creatures had emerged from a small opening on the opposite side of the cave.

Walking more upright than the others had done, it was dragging a large bulk behind it whilst carrying something else in the crook of its other arm.

Having crouched down low to rocky ground avoid being seen, Rose watched it stomp over towards the ship, walking with an almost clumsy stride. Peering down as she held her breath, she caught a glimpse of what the creature was carrying.

Because of their black colour, she did not immediately recognise the two army-issued rucksacks and protective body vests.

Stifling a gasp of horror by quickly covering her mouth with her hand, Rose forced herself to hold it in and did not even risk removing her hand. To make a noise now would mean death.

Instead, she continued to watch as the creature easily reached up and lifted itself up and through the main doorway of the ship, disappearing inside only for a moment to deposit the stolen equipment before it remerged and headed back the way it had arrived.

Even after it had gone, Rose waited a little while longer before turning to the Doctor as she lowered her arm and opened her mouth to speak.

"'I know." He told her. "Not good. Not good at all."

The last time they had seen those same rucksacks and body vests, they had been securely strapped onto the bodies of Peter and Stefan. Now that they were not could only mean one thing. Something had gone horribly wrong and both men were in terrible danger.

The last thing that Peter Argent could remember was that he had been arguing with Stefan.

Well… It was more accurate to say that he had been the one having the argument whilst Stefan had followed after him and listened with his usual unwavering patience. The corporal wasn't one for shouting or storming off whenever the anger of a confrontation threatened to rise up like bile in the mouth.

It was one of the many reasons why they had remained friends.

However, all Peter wanted right now was to be left alone as they reached a fork in their way forward. Barely hesitating as he marched down the lefthand tunnel, he knew that they could always double back should they encounter a dead end.

Somewhere at the back of his mind, however, there was the growing unease that he was moving too quickly and was failing to keep up his observations of their surroundings. With such monstrous creatures on the loose, death could very easily be around the next corner.

But he simply didn't care.

Putting as much distance between himself and the Doctor was his only priority. That was his one goal for the moment because he couldn't and wouldn't stop to think about what the Time Lord had said… What it was that he had discovered…

No! Don't think about it, Argent. Just keep putting one boot in front of the other.

Consciously aware that he was ignoring Stefan, and more specifically the conversation that his friend was trying to have with him, Peter continued to ensure that he was at the front and keeping himself a few paces ahead of him.

"Peter, slow down. Just listen to me." Stefan told him, jogging to keep up. "Mate, listen. It doesn't matter that he knows."

"Doesn't matter!?" He barked back over his shoulder. "Of course it matters! You saw the way he looked at me. You heard what he said…."

"That doesn't mean anything. He of all people will understand."

Stopping so suddenly that Stefan bumped into him, Peter spun around on the spot.

"Oh, because he's an alien too!?" He snapped. "Yes, we're all part of the same club. Of course, he'll understand."

"That's not what I meant, you know it isn't." Stefan countered. "Just calm down, Peter. Take a breath, your eyes are starting to change."

"So what? Let them."

But he did stop and inhale in deeply, blinking a few times until he was sure that his eyes were back to their usual shade of silvery grey. Stefan had seen it plenty of times before, of course. But it had become a habit of his to warn Peter whenever that side of him emerged.

"Okay, fine." Stefan suddenly told him, throwing his arms up in apparent defeat. "Yes, he's not the same as you and might not understand what you are."

"Well, there you go! After all this time, I'm going to get found out."

Peter knew that he shouldn't be shouting, not when the noise could be attracting the attention of any nearby creatures. But old fears he'd had locked away for a while now had suddenly surfaced again, and he didn't know if he was able to put them away this time.

"Let me finish!" Stefan insisted. "Because he doesn't even know what you are yet. Besides, who is he possibly going to tell besides Rose?"

"He's friends with the brigadier!"

"Well, do you really think he'd do that? Rat you out to the world?" His friend reasoned. "Why would he? Because he wouldn't gain anything from it, and I don't think he's the kind of guy to ruin someone's life like that."

Peter said nothing in response to this.

Not once in over seventeen years of friendship had Stefan told him the wrong thing or failed to make him see reason despite his remarkable ability to remain steadfast in his stubbornness.

"Yeah, I guess so." He reluctantly agreed. "It's just... It's getting so hard, Stefan. Keeping it all hidden away and lying to people. It's like half of me is missing, and I… I just get scared that one day I won't be able to cope with that anymore."

"I know," Stefan told him sympathetically. "It's not fair and I know it makes you angry. The Doctor wasn't exactly sensitive about the whole thing either."

"Understatement of the century."

"But just remember, Peter. You don't have to do this alone."

Peter shook his head and looked down towards the ground.

"Thanks, Stefan." He told him. "But it's not what I meant."

Peter had never been able to sum up the words for it. But it was a feeling that brewed somewhere down in the pit of his stomach, rising up like a dull ache regardless of whatever comfort Stefan, Emma or his parents provided. It was the sense of longing for something that he wasn't quite sure even existed or not.

Clearing his throat somewhat awkwardly, Stefan tried to lighten the mood.

"In any case, the Doctor isn't as clever as he thinks." He told him. "He doesn't know everything about you. Not as much as I do, that's for sure."

Peter took the bait and smiled back at him.

"That's because you had a pretty big and very obvious clue as I recall?"

"I guess, but…"

It was the way Stefan looked straight past him that alerted Peter to the danger even before he heard the soft, rumbling growls echo down the tunnel towards them.

It was one of the creatures.

He knew that it must be stood very close to them if Stefan could see it. But the near proximity and narrowness of the tunnel was an advantage to them right now because it meant that the creature had almost no room in which to be able to avoid being shot.

"On my mark, I'll bank left," Peter whispered. "You'll have a clear shot."

Silently, he then mouthed the countdown and dove left towards the ground. Tumbling to the floor, Peter heard the boom of a shotgun blast as Stefan pulled the trigger. But almost at once, he knew the plan had only half worked.

"Damn it!" The corporal hissed. "I think I winged it. Hit in the shoulder."

He had not had the luxury of time to aim and the creature was already bearing down upon them even as he had taken the shot. Sensing the danger, the alien had ducked its head at the last possible moment and shrieked with pain as the bullet had clipped the very top of its collarbone.

Recoiling immediately, it had turned and fled the way it had come.

"We can follow it," Peter announced, jumping back up onto his feet. "It's bleeding, I can smell it."

"Well, get after it then!" Stefan told him. "Go!"

They both took off at a run and it was this that proved to be their mistake.

Even without the torch Stefan was carrying, Peter could see clearly enough to cut a path through the darkness. Stefan was able to keep up by following after him, but neither man was paying much attention to where they were putting their feet, and neither of them had noticed that the tunnel had begun to head downhill.

The ground simply fell away.

Tumbling uncontrollably headlong over sharp rocks and the hard, unforgiving ground, Peter was only somewhat aware that his rucksack was protecting his back as the world span all around him. His hands had instinctively dropped his shotgun in order to move up towards his head in an effort to protect it.

But it wasn't enough.

Trying to stop was impossible and any sense of direction was gone. Peter was never quite sure when or how he lost consciousness. He was still rolling as far as he could tell. It could have been a stray rock or possibly even Stefan's boot that proved responsible for knocking him out.

But one moment he was falling, and the next everything went black.