John had always loved watching Doctor Who when he was a kid, and he never acknowledged the fact that it was the adventure of it that drew him in in the first place. He didn't need to.

He'd dress up as the aliens and monsters for Halloween, and once pinned a piece of celery to his jacket until Harry had made him take it off because she said he looked ridiculous. He made a cardboard TARDIS out of the box from the refrigerator they got when the old one broke, and used it to hide the mess in his room for a year and a half until it started falling apart and he had to throw it out. For years he'd run outside the moment he mistook a car driving by for the noise it made when it materialized, and talked about little else for a large chunk of his childhood.

Afghanistan, he discovered once while jumping out of a helicopter, had the adventure and heart-pounding fear, sometimes, but it didn't have the fun or the same kind of excitement he'd always dreamed about as a kid, but that was okay, because none of that ever really happened and he was fine with that by then.

He felt like Sarah Jane when he was sent back to London and had nothing to do with himself anymore, until Sherlock came along.

Sherlock Holmes was just as good as any Doctor would have been, and sometimes better, because he was real. No one else ever ran around London in the middle of the night chasing criminals and no one else even got close to having the chance at living with his own madman without a box, and no one else could ever possibly give him anything close to the crazymadinsane rush of adrenaline that he got just from tagging along with Sherlock when he had a case. Even when he almost died or found body parts just inches away from dinner in the fridge, it was as close to saving the world with an alien as he was ever going to get, and he was never really quiet about how much he loved it.

He was in front of the television, watching a rerun of one of the newer episodes, Sherlock almost definitely contaminating something in the kitchen, when he finally realized it. He covered up the choked laugh with coughing when Sherlock looked over at him with a frown, and shook his head and turned back to the television until Sherlock went back to whatever the hell he was doing.

Only a couple weeks later Sherlock died, and John realized, in the very back of his mind, that he'd turned into Sarah Jane again with a hint of Amy Pond thrown in, except with just avoiding his psychiatrist instead of biting anyone. He was alone again, no madman without a box, and he didn't know what to do with himself.

He didn't watch any more Doctor Who, either.

Where it counted, he could have been dead and he probably wouldn't have noticed until he couldn't get the kettle to turn on.

But then, three years later, when he'd finally started getting back to being a normal person with a normal life and normal friends and a normal girlfriend (no Sherlock to compete with, this time, and he was toying with the idea of asking Mary that stupidly Big Question he'd always avoided in the past), Sherlock showed up on his doorstep with an apology and an uncharacteristically nervous expression on his face, and everything else faded in comparison again.

Sherlock Holmes might as well have disappeared in a big blue box for three years, but he was back to square one with him within a few weeks, no matter how many times he told himself it would be a bad idea.

Because when you run with Sherlock, it feels like it'll never end. But however hard you try you can't run forever. Everybody knows that everybody dies, and nobody knows it like John Watson.