The Doctor bolted up, clutching his chest, unable to breathe properly. His left heart was beating extraordinarily fast, his right doing nothing at all. Something was seriously wrong. He was travelling alone. Why? Why be so stupid? He needed someone to help him. One of his hearts wasn't beating. He eventually managed to get his breathing under control somehow, the air filling his lungs again. What was wrong with him?

At that exact moment, a certain consulting detective fell clumsily out of bed. His pulse rate was slow. Was he dying? For once, the great Sherlock Holmes had no idea what was happening to him.

"John! John! Something's wrong with me! I think I'm dying!"

"Then die quietly, it's four o'clock in the morning and I have work tomorrow- today!"

"Something isn't right, John! Hel-" his lungs cut out, and Sherlock wasn't able to breathe. What was wrong with him?

Just as John rushed to help Sherlock upon realizing that he genuinely couldn't breathe, the Doctor was using the TARDIS's technology to perform an x-ray on himself. He gazed open-mouthed at the results. He hadn't expected this. This was completely illogical, far beyond reason. Maths, physics, all the timey-whimey things in the world and even his sonic screwdriver couldn't reverse what had happened. He only had one heart. The Doctor was human.

"Oh...oh my God, Sherlock. Even you can't work out what's happened here."

"What is it, John?" Sherlock asked his best friend, genuinely scared.

"I...I have no idea what...Sherlock, you've got two hearts!"

The consulting detective collapsed spontaneously. This defied logic. This was beyond anything that even remotely made sense. He couldn't deduce what had happened in a million years. All sense was useless, wit and sarcasm and clever remarks couldn't help, not when the facts of the world had been destroyed in an instant. Sherlock had two hearts. Sherlock wasn't human.

He needed Clara. He needed Amy. He needed Donna, Martha, Rose, Sarah-Jane. He needed help. He needed his heart back. He needed to find the man who had taken it and get it back, by force if necessary. The Doctor sunk to his knees, head in hands, defiant and determined yet resigned. How had this even happened? Why? Who? What? Where? How? Something was wrong with the world, the universe. Something was terribly, terribly wrong. There was one timelord left, and he didn't even know what he was. The Doctor was human. What should he do? Carry on as normal? Get a job? He couldn't keep calling himself 'The Doctor' anyway, it lost it's charm if there wasn't anything else mysterious about him. He was normal. Ordinary. Boring. He fidgeted with his bowtie, and suddenly had the urge to rip it from his neck and put on a scarf instead. Weird.

Sherlock lay on the sofa, with three nicotene patched on his arm. He wanted to use more but John forbade him to, his doctor instincts kicking in easily. He was also a concerned friend who didn't like Sherlock's habits at the best of times. At least he wasn't resorting to class A drugs as he may have a few years ago. But he did need to think- three patches would usually help but this was more than a three-patch problem. How many patched would it take with two hearts? Six? Twelve? Sixty? He didn't know what he was, why this had happened. Not knowing scared him more than the hound he thought he had seen, glowing red eyes, matted black fur, vicious teeth. This was at least five times as bad; did that equate to fifteen patches? All he did know was that he wanted a red bowtie, for some reason that was beyond him. Maybe the man, thing, alien he had stolen a heart from liked bowties. That was the only slightly logical conclusion he could draw.

They both had exactly the same thought at exactly the same time- I need to find him...

So, that's the first chapter! Feel free to tell me what you think, whether it's compliments or concrit, I love it all. This is just a fun thing I'm doing with a random crossover idea I had, I'll happily write more if it's wanted :)