Contains spoilers for this episode and earlier episodes.
A car bomb outside the Lightman Group brings an old counterterrorism case back to Cal and Gillian. Henry Andrews was on his way to explain what happened to Jimmy Doyle's family when he was killed. Doyle wants answers about the deaths of his wife and young daughter, while officials try to label him responsible for fresh bombings. Cal suspects that the attacks are eliminating people who could expose the earlier operation.
Questioning Richard Prosser reveals that Lightman's assessment helped authorise an attempt to kill Doyle seven years earlier. Doyle's family died instead, and secret recordings of Gillian's sessions with Cal were kept as leverage. Lightman stages a threat against Prosser's wife to force him to speak, with a polygraph distracting him during the confrontation. Prosser identifies the operative called Finch, and Doyle meets the man who killed his family.
Doyle's daughter would have turned sixteen that day. He points an unloaded weapon at Finch but refuses to continue the cycle of revenge. Lightman did not know the gun was empty when he intervened. Afterwards, Gillian explains that she concealed the truth because Finch threatened Cal's wife and daughter before their first session. Cal also admits that he wanted officials to kill Doyle when he originally assessed him. The inquiry exposes choices that neither partner can dismiss as somebody else's mistake.