When an op goes bad, the team must deal with a proverbial monster in their house before it can take them down one by one. Meanwhile, Director Weitz is forced into a tense game of psychological chess as Madeline Burke attempts to assess his loyalty and root out a potential mole at the FBI.

In order to stop a terrorist group from procuring a deadly chemical weapon, the team must remember key details from their first days at the FBI. Meanwhile, Weller worries after he gets scary news about the health of his daughter.