"Are you sure, Rory?" Amy asked him, hoping he'd been wrong. "The Doctor has two hearts, maybe...."

"I know he has two hearts!" Rory snapped at her. He felt so frustrated and distressed that he could do nothing to help. Fat lot of good his medical skills were on an alien like the Doctor. "I checked them both. Do you think I'm stupid? He's gone, Amy. There's nothing I can do." Just then, he felt guilt on top of everything else, for being angry with his wife. He looked at her and shook his head regretfully, then leaned over and kissed her on the forehead. "I'm Sorry. I'm Sorry." Was all he could think to say.

"I'm sorry for the way things are in China. I'm sorry for the chains I put on you...." The Doctor abruptly sang, slightly off-key and in a mumble. Rory and Amy gave a start and shouted, "Doctor!" at the same time. The both of them felt a surge of joy when the Doctor gave a great shudder and opened his eyes.

"Waking up singing a John Denver song. Never did that before. Not sure I want to do that again." He said in a weak voice. "Although, I am rather fond of his nature songs. Very Thoreau-ish. I like Thoreau-ish things. I think. Do I? Yes, definitely like Thoreau, though I do wish he'd installed a bath at Walden Pond. Got a bit minging in that cabin come July. And don't get me started on the loo....Oh, hello." The Doctor said to Rory, looking up and seeming to notice him for the first time. "Why are you holding me? This isn't some sort of kinky newlywed thing, is it? Good heavens, I hope not. I'm not wearing my lucky chastity belt." With that, the Doctor slipped back into unconsciousness again.

A short while later, found them sitting in the control room's jump seat, with Amy on one side and Rory on the other. Rory was just finishing checking the Doctor over with the sonic screwdriver, which the Doctor had pre-set on examination mode. Rory handed handed the sonic back over to the Doctor, along with his torch.

"Antibodies going great guns, elevated seritonan levels, borderline high blood pressure, slight hearts arrhythmia." The Doctor said, checking the readings. "Otherwise I'm in perfect health." He smiled, then gave a little cough. Rory and Amy could see that his face was still very pale, and the Doctor's breathing was shallow and rapid. He told his wife to go and fetch a blanket.

"Is there anything I can do, Doctor?" Rory asked solicitously, after re-checking the Doctor's pulse and respiration. Not that he had any clue as to the Doctor's normal heart and breathing rates. "Can I get you anything that will help?"

"Actually, I could do with a cup of tea, some celery and a pepperoni pizza." The Doctor told him, nodding.

"How could you want to eat at a time like this? Tea, celery and pizza? Is that normal for a Time Lord?" Rory asked, wondering if the Doctor was hallucinating, or merely being himself. "You should be in bed, getting proper medical care."

"What do you need those things for, Doctor?" Amy asked, who'd quickly returned, and was placing a plaid blanket over him in a motherly fashion. She was curious about his sudden appetite, despite her worries for the Doctor's health. Amy could count on the fingers of one hand, the times she'd seen the Doctor actually eating. It seemed he could go days without food.

"Tea and celery, great restoratives, wonderful medicinal properties...well, if you're a Time Lord, anyway. Mind you, celery's a bit rubbish. Though back in Victoria's time they thought it was something quite extraordinary. A horticulturist named Menand wrote an entire book about it. Devoted much of his life coming up with new and improved strains of celery. Very boring times back then. That's why I usually skip that era. Well, that and the fact that Victoria exiled me forever from British soil. And probably the giant rat in the sewers thing, as well. Still, as I said, celery does occasionally have it's uses. I mean, other than something nutritionally otiose to add texture to a tuna fish salad."

"Yeah, so you don't like celery except for its medicinal properties, got that. But, what about the pizza?" Rory said skeptically.

"I'm famished, I could eat a whole pizza pie." The Doctor said, licking his lips hungrily. "And a few sarnies...oh, and maybe a curry, as well." He was feeling quite peckish. Why was he so hungry all of the sudden? Then, he remembered.

"On second thoughts, never mind all that. We need to get out of here!" The Doctor said desperately to his friends, struggling to get to his feet.

"And you need to lie still and rest. You're body is reacting like it's been in shock." Rory told him firmly.

"No, you don't understand. We're in real danger. We've all got to get out of here, right now!" The Doctor gasped. He could feel his face bathed with sweat. His limbs trembled and he felt as weak as newborn blobstachk.

"Is was that green light that was in here, right? It's harmful to you?" Amy asked him. That seemed the most obvious answer.

"It's deadly, Amy. Not just to me, but to all of us. That's why the TARDIS went into emergency shut down and crashed. Her failsafe mechanism tripped when we were attacked in the vortex. Although it's doubtful she could be seriously harmed, she's still alive, and when it tried to attack the ship, the TARDIS reacted accordingly."

"What would've happened if it had attacked the two of us, then?" Rory asked, suddenly concerned for the safety of his wife.

"It bit off more than it could chew, with me, so to speak. Besides having stronger antibodies and a binary by-pass system, I've also been properly vaccinated. But you've never encountered anything like this before, so I'm afraid the split second it came into contact with any humans, it would consume them, wiping them out instantaneously, as if they'd never existed."

"And, what exactly, is this 'it', Doctor?" Amy said. Shivering with sudden apprehension, she looked nervously around the interior of the TARDIS. This wasn't something she liked the idea of, to be trapped in here with some unknown deadly alien.

"'It,' is an intelligent virus, Amy." The Doctor told her seriously. He could feel his hearts still labouring over each of their beats. He had to get away before the illness had another go at him. The Doctor knew he might not survive another attack so soon after the first. "And, an unusually aggressive one, apparently."

Just then, they heard the rumble of a big engine. A back up hooter sounded, its noise muffled somewhat by the sides of the hole. Rory ran over to the doors and peered up through the crack. For his trouble he got a face full of dirt.

"What the hell?" Rory sputtered, jerking his head back away from the doors. "It's alright, I'm fine." He told Amy, who was looking at him with concern in her eyes. He'd only just managed avoiding getting any dirt in his eyes. The bulk of it had landed mainly in his hair, which annoyed Rory. He'd only just washed it that morning. Brushing the grit out of his hair, he said, "There's some kind of heavy machinery up there, digging a trench so we can get out."

About twenty minutes later, a big burly farmer and the old woman helped Rory and Amy get the Doctor up out of the trench. Per the Doctor's strict instructions, Amy made sure the TARDIS door was locked behind them.

Elisabeth thanked her neighbour for his help. The man, whom had been introduced as Lester, was surprisingly stoic about the incident. He'd reckoned the whole thing was likely some sort of prank by some boys from the local public school down the road. He'd told Elisabeth that he'd fill in the hole for her, once the authorities came along and removed the box. Declining her offer of tea, he drove off. The four of them watched as the man drove away in his backhoe. Its two red lights on the rear and the growl of the machine, made it seem like some mechanical monster, reluctantly backing away from them and slowly bumbling off into the night.

Seated comfortably on the sofa in Elisabeth's sitting room, while she put the kettle on for tea, Rory felt the Doctor's pulse again. He got his hand slapped away. "What'd you do that for? I'm only trying to help." Rory said, feeling hurt.

"I know, I know, Rory." The Doctor told him, "But I'll be fine, I promise." 'As long as I don't come into contact with that virus again.' He thought to himself.

"What is this virus thing? You said it was intelligent, how can a virus have intelligence? That just doesn't make sense." Amy plied him with questions. She thought that if he was feeling feisty enough to slap down Rory, he probably was well enough to shed some light as to what was going on.

"It makes perfect sense, Amy, you're just thinking one-dimensionally, with your human ideas of what constitutes sentient life. I's called the cipher flu," he informed them, stretching his tired, recovering body out on the sofa, "so called because when it first appeared a dozen millenia ago, no one knew where it originally came from, or how it migrated from worlds to galaxies, through space and time itself. The only sign anyone gets of the infection's presence, is an atmospheric disturbance, usually in the form of severe thunderstorms, caused by the electrostatic charge given off by the virus. That, and the green lightning."

"You said there was a vaccine, so you must know something about this thing." Rory interjected. He noticed that most of the colour had returned to the Doctor's face, and that he appeared to be almost fully recovered, other than looking exhausted.

"All anyone knows," the Doctor nodded, "is that it's some kind of living electrical charge, infused with a deadly bacteria. It seems to know how to attack a world without initially drawing attention to itself. It specifically feeds off the electrical impulses in human or humanoid brains. Unfortunately, it does so with such force, that it disintegrates the rest of the body. Bit like standing near an atomic blast, I suppose. My people developed a serum which can counteract the electrical charge. Turns the positive energy into negative and effectively drives the virus off. Unfortunately, it only works on Time Lord physiology."

"Kettle's on!" Elisabeth announced, poking her head around the doorway. She walked over and turned the television on. "I'm going to be a bit longer in here. Just putting some finishing touches on some sticky buns I made earlier today. Thought you might like a little something with your tea. Feel free to make yourselves at home. You can watch a bit of tele while you're waiting." Turning on the news, she quickly bustled out again.

"I just hope we can keep it contained inside the TARDIS." The Doctor said softly, as soon as he was sure that Elisabeth was out of earshot.

"Why? What happens if it isn't?" Rory asked, abruptly alarmed.

"I suppose," The Doctor said, suddenly looking very old, for someone who looked so young, "that people will begin to disappear under mysterious circumstances. Possibly only a few at first, that's what usually happened on many of the planets this virus infects. But then," he continued somberly, "they'll begin to be extinguished en masse. Whole worlds have been decimated by the cipher flu, their populations gone within a week or two, billions of lives, snuffed out as if they never were."

"You don't think that can happen here, do you?" Amy asked, suddenly feeling another shiver running down her spine. "That we could have brought this thing to my own planet?"

"No, no." The Doctor said, although a trifle uncertainly. "It's still trapped inside the TARDIS. Nothing can get through those doors once they're locked."

Elisabeth came in just then, with a tray loaded with tea and sticky buns. The four of them settled down to watch. Amy tried not to be embarrassed when the Doctor gulped down his tea and bun. The Doctor was about to help himself to another bun, when she saw his face become pale and drawn again. He was staring at the television screen. Amy turned her attention on what the news presenter was saying.

"Some unexplained disappearances, under very mysterious circumstances, in two different parts of the country have left police baffled today. Two young men in Wales, returning home from a concert, apparently went missing during what a witness described as a sudden violent thunderstorm. Earlier that day, the entire staff of a call centre in Milton Keynes, with the exception of a single person, completely vanished, also during an unexpected violent storm. Police are questioning the sole remaining staffer, but so far are unable to come up with any leads or explanations for the mass disappearance. Weather experts also are at a loss to explain the violent storms, as no such weather pattern was predicted for either of these locations for today. One witness described the storms as 'freakish,' claiming to have seen green lightning. Police insist that they are taking this very seriously, and while not ruling out the possibility of criminal activity, they suggest it may all be simply some sort of joke or publicity stunt. Tune in tomorrow, when we'll have more on this breaking story on 'Breakfast'."

"Oh, no, no, no, no! What've I done?" Amy heard the Doctor exclaim. She turned and saw him with his head in his hands, bent over his knees, almost on the verge of tears. She placed a hand on his back, rubbing it gently. Trying to console him, she told him that it wasn't his fault, but at that moment he was inconsolable. "Amy," he told her, his face etched with grief, "I'm sorry, I'm so, so sorry."

"What for?" She asked, not sure why he was so upset.

"I fought for this planet so many times." he said, tears forming in his eyes, "From Daleks, the Cybermen, megalomaniacs, gods, would-be gods, alien all-sorts, even my own people. But, never once did I ever imagine that I would be the one to cause Earth's own destruction."

"But, you haven't done anything. You didn't bring us here on purpose. You didn't know the virus was going to attack the TARDIS." Rory told him. "Even if this virus thing has found its way to Earth, you can find a way to stop it, can't you?"

"No, Rory, I can't." The Doctor said softly, with cold dread in his voice. He'd lost one home. Now he was about to lose another. "I don't have a clue how to prevent this from attacking humans. I'm afraid this time, you're all as good as dead."