 The task force comes under intense scrutiny when the FBI suspects that an insider is selling covert information. Bailey agrees to a mock field training exercise designed to root out the mole, where he learns that one of the agents, Art Behar, has a personal grudge against him for being involved with Behar s ex-wife, Ellen. When one senior investigator, Ed Portero, is found murdered in the command center, Sam tries to profile which one of the team s edgy members might benefit the most from trading FBI secrets. Meanwhile, Grace goes public with the news that she s pregnant, and Nathan stands at the crossroads of the future of his bumpy marriage with his lawyer wife Michelle.