Sherlock agrees to take a case from a man claiming to be Moriarty, hoping it will bring him closer to finding his nemesis. Meanwhile, Gregson encourages Joan to give up…

When a person of interest is poisoned, Finch and Reese only have 24 hours to identify the toxin and find the person responsible; Detective Fusco’s past catches up to him.

The battered body of a five-year-old girl in foster care is discovered, and suspicion soon turns to the girl’s foster brother, who is into violent video games and doesn’t seem…