While watching an illegal street fight, Cal says one of the fighters, a man named Orlando, is dead from the neck up. Seconds later, he's down.
Cal walks the winner, Raoul, to his car and demands his keys. Raoul scratches Cal, who grabs the keys. A man upstairs sees this. Raoul tries to catch a bus but lacks the fare. When Raoul returns to his car, he's killed.
Meanwhile, Gillian is in bed with Dr. Burns, who gets a text message: "Marco. All set for tonight." Rummaging through his drawers, she discovers a passport issued to Marco Gianelli.
Later, FBI honcho Bernard Dillon -- now in charge of Ben and the Lightman Group -- visits the office. Dillon is investigating Raoul's murder; there's camera phone footage of the fight. But his main interest is Ron Marshall, who bankrolls the fights. Cal and Dillon have some history, but both say they've moved on.
Cal asks Orlando's manager, Simone, if Orlando killed Raoul because he lost the fight. Simone denies this and wants Cal to prove it.
Ben tells Cal they found skin cells under Raoul's fingernails. Cal tells Ben that he was with Raoul the night he was murdered and wants Ben to delay the test results because he needs some time. Cal is afraid that he'll be arrested and lose custody of Emily.
When Ria finds Cal's face in the fight footage, she deletes that sequence, asks Eli to take over, and tries to call Cal.
Cal meets with Marshall, who's holding Orlando prisoner, and explains that his interest in the fights is purely scientific. Orlando denies killing Raoul, but Cal is not sure. Then Ria shows up. Cal denies knowing her, and Simone covers for them. As they leave, Ria tells Cal she cut him out of the footage.
Gillian gets a surprise office visit from Dr. Burns, who cancels their evening plans because he has to interview some potential foster parents.
Ben has just called off the rush order on the skin cell tests, when Dillon enters. Raoul's brother is here. Raoul's brother says Raoul left Peru because he argued with their father. Raoul wanted to be rich; their father thought he was irresponsible.
After starting a fire to cause a distraction, Cal and Simone enter Marshall's warehouse and free Orlando. When Cal asks why he killed Raoul, he looks at Simone, who denies killing Raoul. Noticing Orlando's shame, Cal accuses him of throwing the fight. Orlando says Raoul told him the Shining Path guerrillas were after him. This was going to be his last fight before he left town and he needed the money, so Orlando let him win.
Dillon learns about the skin test delay and puts it back on track. Meanwhile, Eli discovers there's footage missing, so Ria says Cal has a rush job for Eli, and she'll take over. Then Dillon wants Cal to question a person of interest, but Cal is not there. Ria volunteers. It's Marshall, who recognizes Ria -- and denies everything. Ria says he's not lying; Dillon knows something's up.
Gillian is in her office, checking up on Dr. Burns/"Marco," when Cal enters. Gillian asks him to butt out. Dillon says they've got a murder witness with a history of drug abuse and wants Cal to question him. Cal asks Gillian to do it, and the witness (the man upstairs) says the suspect looked like Cal. And when he passes Cal in the hallway and positively IDs him, Cal says he was with Ben that night. Ben covers for him.
Ria asks Cal to examine the phone footage. At one point, Raoul looks away from Orlando and shows fear because he sees a man leaning against a car, relaxed. He's not there for the fight.
Meanwhile, Ben tells Gillian that anyone who charters a boat from Baltimore for five hours is probably a drug smuggler. Gillian says she's just checking for a girlfriend. Ben says he'll need a passport or a cellphone to learn more.
Cal shows Dillon he was at the fight, and admits knowing Raoul, explaining he withheld this information because of their past history: One of Cal's reports prevented Dillon from being promoted, and Cal was afraid Dillon would take this opportunity for payback. Cal then shows Dillon a photo of the man leaning against the car.
Gillian is at Dr. Burns' place, looking for his passport when he walks in, passport in hand. Burns says the passport is for work; he can't say more. Gillian wants the truth or she's leaving. Burns says he's a DEA agent, working undercover at Covington, monitoring gangbangers linked to a drug cartel. He is a psychologist, and he didn't lie to her -- except about the foster parents' meeting -- and his real name is Dave Atherton. They hug.
The car was rented by Raoul's brother, Juan, whom Ben brings in for Cal to question. Juan is a revolutionary; so is his father and so was Raoul, who was fighting to fund the revolution. And he didn't kill him. Dillon orders Juan released.
That night, Orlando accosts Juan on an empty street. The FBI is observing, feeding Orlando questions, which he repeats in Spanish. When he asks why Raoul was happy to go home, Juan's snarled answer says everything. Agents swarm and handcuff Juan.
Back at the office, Gillian introduces Dave to Cal, who says to handle her with care. Gillian says Cal could've told her what was going on. Cal says he doesn't share -- and walks away.