One day, John has a dream about Sherlock.
He'd barely slept the night before, spending time with his girlfriend. His ex-girlfriend. They were trying to patch things up, John laughs bitterly on his way home when he thinks about it. He wonders why she dragged Sherlock into it. Then he tells himself not to be stupid. He knows exactly why she dragged Sherlock into it. He doesn't look too far into it though. He doesn't want to do that yet, not yet.
It doesn't surprise him that the coffee he drinks back at the flat isn't enough to keep him awake. Sherlock's gone out so John just curls up on the couch, telling himself he'll just rest his eyes for a second then he'll brave the horrors of the fridge and try and make lunch.
He wakes up at three in the afternoon, five hours after falling asleep. He wakes up sweating. He wakes up screaming.
Once he's aware enough he realises that Sherlock's come back to the flat, and the man is staring at him. Hypnotising with those ice-blue eyes.
Sherlock asks him if it was Afghanistan again.
John blinks, for a split second of thinking time, thinking of his dream. Thinking about the images that seemed to be burned into his eyelids. Sherlock at the pool. Sherlock with Moriarty. Sherlock, face down in the water. Sherlock getting turned into a sieve by the bullets. Sherlock bleedingbleedingbleeding...
John finishes blinking and looks up at Sherlock, looking into those ice-blue eyes.
He tells the detective that it was Afghanistan.