The death of Shinwell (Nelsan Ellis) spurs Watson (Lucy Liu) into taking up the man's crusade. While suggesting a level of caution, and with far more mixed emotions towards the recently departed than what he knows what to do with, Holmes (Jonny Lee Miller) proves equally up the challenge of the case although in his case he is distracted by a B-story which feels largely out-of-place shoehorned in here. One of the effects of having Holmes and Watson work for the police is they rarely choose their own cases. In this instance the episode is fueled by Joan's need for retribution for Shinwell's death which leads them to confront the apparent head of the gang and his upstanding brother who actually knows far more about its inter-workings than it appears.
At the tail in of the season the show introduces a dangerous threat to Holmes and Watson, one who is willing to sacrifice even his own brother to keep himself out of prison. Distracted for much of the episode by an old case on which he barely consulted which has resulted in the convict's suicide, "Scrambled" introduces Joanna Christie as a woman from Sherlock's past who has begun to re-insert herself into his life, his sobriety program, and his cases. Her connection to Holmes appears to be quite complicated. The episode ends on an ominous exchange between the pair which would have worked far better had the character been set-up earlier in the season, instead the entire subplot feels rushed and, at times, poorly executed.