Sherlock is silently cursing the layout of 221b. He's lying on his bed, on top of the covers looking at the ceiling. Looking at the cracks around the light fitting, the cobweb in the corner. He can't sleep.

He can't sleep because he knows that three point five metres above him, two point two metres to the left, Doctor John Watson is also laying in bed. John is asleep. Sherlock knows this because he heard the gentle purring of John's snores when he tiptoed up the stairs tonight and listened at the door.

He can't sleep because he knows that John is wearing those cute pyjamas with the checked trousers and the long sleeved t-shirt. He knows that the t-shirt will be rucked up a little where John has wriggled in his sleep. Rucked up just enough that, if he were to go in to John's room he would be able to see a few inches of the exposed flesh of John's belly, with a trail of sandy hair leading down in to his trousers. And he knows the flesh would be warm and soft if he were to reach out and touch it.

He can't sleep because he knows from every sound, every slight movement or creak of the ceiling what John is doing, which way he is turning. Where exactly he is in relation to Sherlock.

Every night when he can't sleep he climbs the stairs to John's room. He stares at the door, listens to the soft sounds of John sleeping. Sometimes he hears the harsh sounds of John's nightmares, the sound of tears as he sleeps. But Sherlock never dares to open the door, to walk the short distance to John's bed and slip in beside him. Because he has deduced that John would think that was a lot not good.

Every night he walks back down to his own room. Every night. And he can't sleep.