When undercover FBI agent Mike Warren gets assigned to a California beach house, he learns that his new job requires him to do much more than investigate criminals.
Briggs and Mike turn rival gangs against each other; Mike finds out that his new undercover life comes with ethical dilemmas.
Briggs calls on the house to help Lauren with her case against the Russian Mafia and Charlie gets into some hot water when her C.I. proves unreliable during a dangerous drug deal.
Despite Briggs’ hesitations, Mike gets recruited by a Nigerian drug lord to teach gang members how to shoot well, while Paige recruits Jakes and Tuturro to go undercover with a flirtatious and dangerous female pot farmer.
While Mike gets deeper into Bello’s organization, Briggs and Charlie resume their former identities as a sexually-charged couple to get intel on a mysterious drug supplier called Odin
Mike convinces Bello to steal from the most powerful drug cartel in Southern California and calls on Johnny's unique underwater skills to help. Briggs helps Charlie go to extreme measures to cover-up her bad decisions in the aftermath of a bust that went very wrong.
Dark secrets are revealed when Charlie decides to tell the house about the aftermath of her bust. Briggs is finally forced to come clean to Mike, but just as Mike thinks his investigation is coming to a close, Briggs has a much darker secret up his sleeve.
The newly formed Briggs-Bello alliance is tested when members of the Caza Cartel head north with a deadly ultimatum. During the aftermath, Mike is forced to push his own limits for the good of the case.
Bello's last strike to the Caza Cartel sets a war in motion that Graceland now needs to stop. While on her hunt for Odin, Charlie meets an unusual ally and Briggs comes face to face with the past.
Tempers flare and relationships are pushed to the brink when Charlie discovers a secret about Briggs and begins working with a Federale to find the truth. Mike discovers that Juan is missing and that the FBI has a suspect: Paul Briggs.
Looking for the truth about Juan's disappearance, Briggs and Mike play a dangerous game of cat and mouse- forcing Briggs to make a major decision about his future.
In this season finale, the infamous Caza enforcer Jangles takes a member of Graceland hostage and the house must come together in order to save one of their own from a sadistic killer.