The Cold Case {Sherlock/Johnlock}

Sherlock is drawn to a notorious case- closed and cold, with no apparent leads. John is willing to follow, but his own secret difficulties, paired with the stress of keeping them from his flatmate, begin to take their toll on him.

And in typical form, the two prefer to immerse themselves in the crimes of years ago than talk about things... Which leads to a hated new co-worker who Sherlock views as an imposer, a break-in that no one can explain, and a mounting confusion between the detective and John- with consequences more serious than anyone could ever have anticipated.

(set around series 1/2)