Sydney goes undercover in a mental institution to get information from Shepard, a man who has been unconsciously programmed to be a deadly assassin. Meanwhile, after Sydney becomes convinced that her father was responsible for the death of her mother 20 years earlier. Will discovers the true identity of the woman who claimed having an affair with Danny and Francie is relieved to learn that Charlie is not having an affair other woman. Marshall finds the computer worm planted in the SD-6 mainframe by the CIA.

Sloane begins to question where Noah's true allegiances lie, as passion ignites between Sydney and Noah. Meanwhile, Sydney continues to uncover new information about her mother, which disturbes Jack. A rogue assassin known as the Snowman is dispatched by K-Directorate to kill Khasinau, a.k.a. "The Man." Will and Francie confront Sydney about the mysterious airline ticket stub found in her jacket.