Post HLV Sherlock is sexually assaulted, in a random attack (jumped walking down the street or whatever the OP can come up with). Everyone reacts in a different way. Sherlock continues to concentrate on his work and denies that anything is wrong (even though he is clearly not coping). John and Mary are desperate to help him, in any way possible. Mycroft is utterly devestated that this would happen to his beloved little brother. Lestrade is determined that the attacker(s) be brought to justice. Moriarty finds out and is furious that his nemesis would be hurt in such a way and vows to track down the attacker(s), himself.
Would prefer no Johnlock (Sherlock/Lestrade is ok but no 'healing sex' thanks :))