Sherlock and Watson investigate a child abduction case involving a serial killer known as The Balloon Man, who leaves signature balloons at each of his crime scenes.
A crucial agent crumbles under emotional distress and threatens to topple a valuable network of KGB informants; Professionally, Philip and Elizabeth are tasked with infiltrating the FBI's new communications encryption system.
After a pro-life loner stalks and shoots a doctor, the detectives surmise the gunman has another target in mind and rush to stop him.
Tony's son AJ is suicidal over his break-up with Blanca, and Christopher falls of the wagon with catastrophic consequences.
Tony attempts to repair the rift between New Jersey and New York, while AJ's struggle with depression continues, and a New York associate crosses the line with Meadow.