Contains spoilers for this episode and earlier episodes.
An illegal fight ends with Raoul dead, and Lightman's presence that night threatens to make him a suspect. He had taken Raoul's keys to stop him driving, leaving physical evidence that could connect them. The FBI's Bernard Dillon investigates both the murder and the people financing the fights. Cal fears that their professional history will turn the evidence against him and endanger his custody of Emily, so he conceals his involvement.
Torres removes Cal from phone footage, and Reynolds delays testing skin cells found under Raoul's nails. Their attempts to help make the investigation more dangerous for everyone. Lightman frees fighter Orlando from the promoter holding him and learns that Orlando deliberately lost to let Raoul earn money to leave town. Footage then reveals a frightened reaction to Raoul's brother Juan. Cal finally tells Dillon the truth, and a monitored confrontation with Orlando exposes Juan's role in the killing.
Gillian has a separate reason to question someone close to her after discovering an unfamiliar passport in Dave Burns's home. He eventually explains that he is working undercover for the DEA and identifies himself as Dave Atherton. His supposed foster-parent meeting was a cover for that work. The disclosure lets Gillian understand the immediate deception, while the office's attempts to protect Cal show how quickly loyalty can become concealment during a murder inquiry.