Warning: Diverges from canon. Possibly unlikely circumstances and decision-making, but that comes with the crossover. I did my best to keep it as close to cannon as possible but it may not be entirely accurate, especially sciencey bits. I should also note that this is written in the present tense, and it's my first time doing so... I'm sort of experimenting with different writing styles. That being said, there may be some mistakes (as much as I've tried to proofread it). If that's the case, please don't hesitate to point those out to me. Lastly, there may be potential SPOILERS.

If this isn't your cup of tea, then you may not want to continue reading.

If it is, I hope you enjoy.

Part 1 of 3:

The Forsaken World

The Doctor cannot save everyone, nonetheless...

Something is very, very wrong with this Earth.

It isn't an immediate observation. Of course, he is aware that this is a parallel universe, courtesy of the crack in reality he'd managed to fly the TARDIS into. He isn't too concerned about it (although the journey through the Void is an experience he'd rather not repeat). He firmly rejects the thought that perhaps he doesn't care because he has nothing left to lose, in his own universe. Either way, he's somewhat confident that he will find his way back. This sort of situation usually has a way of working itself out.

So, the Doctor indulges in his curiosity of how different this universe is from his own.

From his place on the TARDIS, he barely glances at the screen which displays a strangely quiet neighborhood before he rushes to exuberantly swing the doors open, as he usually does. He takes a deep breath of air from his (debatably) favorite planet, no matter which universe he's in, and nearly gags at the air which greets him – thick with pollutants, as expected, yet disturbingly overpowered by the scent of rotting carrion. He immediately pulls the doors to a close, eyes watering as he chokes, while his lungs attempt to expel the horrid air particles that swirl within him.

It is the first sign of things gone awry.

After calming down some, he walks straight to the console and mutters about the possible causes behind such a ghastly odor. The Doctor thinks that there couldn't be much difference between the Earth he knows and this alternate Earth. He fervently begins to push buttons, pull levers, and occasionally hammer certain areas (which earns him more than one spark of discontent from his Old Girl). Just to be thorough, he runs every assessment scan available to the TARDIS, which is quite a few.

He becomes increasingly dismayed as the results appear on-screen.

"No, no, no! That can't be right!"

The readings... indicate virtually no signs of life within a twenty-five mile radius, other than six signatures. But it doesn't make sense. The scans were taken in what appears to be a fairly normal neighborhood, aside from the abandoned cars and scattered litter. Which is strange, now that the Doctor thinks about it.

Baffled and unwilling to accept the alarming implications, he runs the scans again. And again. And again.

Perhaps once more?

His stomach sinks as the same results come back.

"Impossible," he breathes, beginning to pace and tug at his hair. "System's working fine, scans are consistent..."

For a moment he considers that he is mistaken, that he's somehow landed on a planet similar to Earth. He quickly discards the thought after his ship promptly flickers the lights in irritation. So, definitely Earth, circa 2010...

The screen on the console beeps, which draws his attention.

"Right then, make that 2011. So," the Doctor clasps his hands together, and his mind works furiously to solve this disturbing riddle. "What happens in 2011? Come on, think."

He considers then discards so many dates and events, people and places – and he closes his eyes to channel his concentration accordingly. He ignores the slowly forming headache, the doubt which blooms in his hearts, and the hopelessness that threatens to drown him. Logically, he knows that it may be impossible to pinpoint which human decision led to this parallel universe, but he is determined to learn what the issue is and find a solution for it. He must. He is the Doctor.

But there are simply too many factors to take into consideration.

He can't help but try.

He ventures outside the ship (the offensive smell remains just as strong) to the familiar land of England, and searches for signs of any remaining government organization. In times of crisis, as this appears to be, there are always contingency plans to counter the event in progress. Although he may not agree with who they deem important to protect – focusing their attentions on political figures more than civilians – the Doctor is determined to assist them. So, he makes his first stop at the Torchwood Institute in Cardiff, hoping they may have some indication of what exactly has happened to the world. To his dismay, there is only an abandoned storage area and the same went for all other branches. Resolutely pushing his alarm away, he tries to find the UNIT Central Control in Geneva... only to find nothing. He then draws a startling conclusion: they don't exist in this universe.

Now he is desperate and tries to find any semblance of authority to confer with. Or anyone at all, really.

It isn't long before he comes across a few humans, near the neighborhood he initially materialized in, but his relief for their survival is bittersweet when he is nearly axed in half by a frightened girl with a heart-wrenching resemblance to one Rose Tyler. The panicked group consists of several young men and women, aside from two older gentlemen, who are pointing makeshift weapons at him (he struggles to keep from staring at what seems to be dried blood stains).

They are visibly confused and suspicious when he asks them what is happening, but they warily indulge him anyway. It is then that he learns of the undead and their threat to mankind. To put it mildly, the Doctor is appalled and repulsed by the things he hears, further nauseated by the thought of what most people would have to do to stay alive in such a situation. Although his love for the human race runs deep, he knows that when they are backed into a corner... the results aren't pretty.

When they demand to know who he is and what he wants, the Doctor tells them the truth and urges them to join him on the TARDIS. He nearly breaks down when they immediately refuse – they whisper that he's gone off his rocker, that he's trying to trick them – and they won't even follow him to see his ship. He begs them to reconsider, to give him a chance to save them, but the group is unanimous and steadfast in their decision. They are much too tempered by their experiences to accept a stranger's promises of safety. It takes a threat of bodily harm for the Doctor to finally, reluctantly take his leave.

As he continues to travel, the Doctor bears witness to horrifying and tragic things. It is so much worse than he is led to believe.

Entire cities, left abandoned or destroyed or both, are either silent or filled with the chilling moans of the undead. He watches their lethargic and unnatural movements, but unable to look their rotting skin or missing limbs for any extended period of time. They truly are moving corpses, and the Doctor finds himself silently mourning for all the lives lost. He wouldn't wish such a cursed existence on anyone, not even his worst enemy.

As for those still living; his brilliant, creative humans... most, if not all, are reduced to something more primal and violent, in order to escape a horrid death in this cruel world. Without law and order to keep them in line, without the comforts of modern technology, and without the certainty of being able to meet their basic needs, they resort to savage and cruel measures to ensure their continued survival. Sometimes, he finds people who do things simply because they can and there is no one to stop them. Their morals are all but forgotten, if not abandoned entirely. People of that sort, the Doctor learns, are capable of truly unspeakable and callous acts. They are nothing more than husks of their former selves, which make them ironically, unnervingly similar to the undead. Oftentimes it is worse, for the fact that they are aware of their actions. It's inhuman.

He wants to stop it, to reverse time, but he knows that he can't. Instinctively, the Time Lord senses that he cannot travel back to prevent this, this sickening event because it is a fixed point in time. He cannot even try without the risk of making matters worse, like the time he'd done in his Tenth incarnation. The entire world is rotting, and there is nothing he can do. He is helpless. With all of space and time at his fingertips, he is helpless.

It finally sinks in that the Earth he knows and loves truly is a universe away.

And it's suddenly too much to take in. Too much horror. Too much suffering. Too much, too much. The Doctor quickly retreats to his ship, defeated, disheartened, and trying to cope with what's happening to his beloved planet and his beloved humans. It doesn't matter that this is a parallel universe; he can't help them, he's failing them, and it breaks his hearts. Absolutely shatters them.

He collapses near the console, overcome by despair. His breath comes in sharp gasps and his eyes burn with tears that never fall. "Why," he hoarsely whispers to himself. "Why can't I do anything?"

He continues mumbling and moves to lean against the console, dimly aware of the lights dimming to a softer, soothing blue. But the Doctor is beyond comfort. He is trapped in a parallel universe that he wishes didn't exist, and such thoughts fill him with disgust and guilt because he is supposed to save people from the awful things he's seen but without an enemy to face, to fight, to erase how can he save the humans from themselves andplease he can't do this –

The Doctor releases a shaky breath as he attempts to compose himself. He feels dangerously close to madness and there isn't anyone to ground him.

"Okay. Alright. Okay. Okay," he buries his head in his hands. "Stop thinking. Stop."

It makes little difference to the storm that rages within, but it does become a bit more bearable. It helps when his dear TARDIS reaches out and provides a warm presence in the back of his mind. The Lonely God feels less so.

For a long moment, he focuses on the simple task of breathing. Inhale. Exhale. Inhale. Exhale. Inhale. Exhale.

He manages to stop trembling – he doesn't remember when he started – and the Doctor attempts to evaluate the situation. Only one thought rises above all others, one that he manages to whisper aloud.

"The human race is facing extinction."

He firmly repeats this truth, a mantra that moves him to his feet. He feels the despair returning but, this time, uses it to fuel his resolve. It is a slow process, and he can't tell if hours or days pass. Eventually, he feels a bit more steady, even if he is nowhere near alright. He doesn't think he will ever be the same after this. He isn't ready to face this world but, for now, he has no choice. He must persevere and piece himself back together.

In all his years, the Time Lord has never felt so weary. He sighs and rearranges his bowtie, a nervous tick he isn't sure when he'd adopted, as he chastises himself. It was time to stop wallowing and actually do something. He first addresses his lovely TARDIS quietly. "Glad you're with me, dear," he pats his ship fondly, before he clears his throat. "Right. Now then, what should our plan of action be?"

The answer comes to him more quickly than he anticipates. While the world at large is too far gone, that doesn't necessarily mean there isn't anyone left to take aboard his ship. Even if there is only one person left worth saving... he will scour the Earth to find them and bring them to safety. The next moment has the Doctor in a flurry of movement, once more pushing buttons and pulling levers with more purpose than he ever recalls having. This, at the very least, is what he can do. The console pulses warmly beneath his hands.

He tries to avoid the sort of people who had driven him away in the first place, whenever possible, and is immensely thankful whenever he does meet a group of the good sort. But that is where his gratitude ends.

Much like the first group of survivors, nearly everyone doubts him. They cannot believe that he would offer them sanctuary without any ulterior motives, and ultimately choose to make their own path (usually not without making their hostility known). Those few who miraculously give him a chance, who cautiously follow him back to the TARDIS, are awestruck and overwhelmed by his Old Girl. He smiles as they gasp and cry out in disbelief, uttering the expected "It's bigger on the inside!" without fail. He sees hope alight in their eyes for a moment, before it flickers and dissolves into dark misery.

They explain that they can't stay or they won't go with him, no matter how much they want to, because they need to find someone – whether that someone is a family member, a friend or, rarely, an enemy. Still, he tries to convince them to stay. Some consider, on the condition that he helps them find their Someone, but the Doctor can't make any promises.

When he realizes the futility of trying to persuade them – because he would never force them – he feels helpless and searches for an alternative. If he cannot save them in this way, then he can at least provide them with the supplies to survive a bit longer, to give them a chance. He offers them food, new clothes, tools (no weapons, to the disappointment of many), and even a shower. Whatever they happen to need, the TARDIS gladly provides it. He also adds that they may rest peacefully for a night to gather their strength, but it seems their trust doesn't extend that far – one man bluntly tells him that he doesn't trust the Doctor to kidnap/rob/kill him while he's asleep. It is hurtful to hear, but he understands that no one would submit to the vulnerability of unconsciousness under someone they do not trust.

Even so... he will forever cherish their watery smiles, their grateful embraces, or their gruff mutters of thanks as they bid him farewell, even if it is often a painful experience. He doesn't want to send them back to the many dangers outside his ship, but he respects each of their decisions. It is a small comfort that these people will leave the TARDIS more equipped to face the world than when they had arrived. He hopes it will be enough to help them live as long as they can.

And as the Doctor continues to press on, he is unaware of the rumors that begin to spread about the Saint in the Blue Box.