Spoilers for this episode.
The nuclear missile is airborne, and CTU cannot track it because of its stealth technology. Marwan refuses to help Jack find its target, insisting that the attack has already served his purpose. His men attack while agents are loading him into an SUV and free him. CTU loses another chance to question the man behind the attacks. A number on Marwan's phone provides a new lead: Richard Heller's cell phone called him a week earlier.
Audrey pleads for a chance to question her brother before Jack applies pressure. Richard initially denies knowing anything, then tells his father about a couple he brought home from a bar. The woman may have used his phone. CTU discovers that the call activated surveillance, allowing Marwan to learn about Heller's private visit. A taxi driver traces the couple to the Mercerwood complex, and Jack asks Tony to join the search.
Tony tells Michelle they must leave CTU if they are going to rebuild their relationship. She agrees before he leaves with Jack. At Mercerwood, Mandy hears the approaching helicopters, kills her companion Gary and prepares to escape. Jack finds the body while Tony and Castle cover the roof. Mandy wounds Castle and uses him to force Tony to surrender. After Tony offers himself as the hostage, she kills Castle and takes Tony away. Jack finds the dead agent and warns CTU that Tony is missing.