When Sherlock investigates what appears to be a series of murders at a top Wall Street firm, he may himself fall foul of a sociopathic slayer. Joan is set up on a blind date and shows investigative instincts.

Joan investigates her first solo case when a wife disappears. The missing woman left behind a tear-filled video that mentions a murder on a subway platform. While Joan searches for the vanished lady, Sherlock probes the murder.

When Holmes and Watson set out to track down a civil contractor who leaked classified information, their lives are disrupted when they are targeted by the group of cyber-activists protecting him. Meanwhile, Joan takes the advice of a friend and signs up for an online dating service.

Holmes and Watson find themselves in the middle of a civil war being fought on the Internet when a member of Everyone, the anonymous hacker group they periodically work with, is murdered.