Young, idealistic officer Kyle Craig is tapped to go undercover in an elite squad of the LAPD where he partners with a morally ambiguous veteran detective.

The rift between Kyle and Frank grows when Kyle refuses to adhere to one of Frank's morally ambiguous rules, but the pair must put aside their differences when they learn the notorious hitman known as "El Cucuy" is targeting members of the Russian mob in Los Angeles.

When Frank's longtime friend and informant is killed by Yakuza assassins, his quest for revenge puts him and Kyle at odds with an FBI agent whose operation against the Yakuza is jeopardized by Frank's actions.

Deputy Chief Lockhart opens an internal investigation into a past shooting which could cost Frank his badge and freedom, forcing Kyle to help Frank clear his name or risk losing the one man who could help him solve his father’s murder.

An investigation into weapons trafficking becomes personal for Tommy when an old friend becomes connected to the case. Also, Lockhart demands to see results from Kyle’s investigation into Frank’s actions, leading Frank to reveal surprising information to his trainee

Kyle’s morals are put to the test when Frank involves him in a plan to take down a criminal defense attorney who has been helping his clients eliminate witnesses.

The hunt for a father-and-son crime team becomes personal for Frank, who is forced to face the parallels between the duo and his own childhood as the son of an outlaw.

Frank and Kyle seek justice for a community organizer who is accidentally killed in a gang-related shooting.

Frank and Holly’s worlds collide when several of her call girls go missing, leading the SIS to investigate an eccentric, reclusive Hollywood producer.

The hunt for a suspected terrorist takes an emotional toll on Kyle who is convinced that he encountered the suspect during his service in Afghanistan.

Kyle’s trust in Frank is shattered when he learns that Frank has been lying to him about the circumstances surrounding his father’s death.

Kyle, Tommy and Rebecca must rescue Frank when he goes on a rogue mission to Mexico to locate intel linked to the murder of Kyle’s father.