When one of Charlie's mentees from the local library gets mixed up with a gang, Charlie ropes in the whole team to help save her life. As Bill's term draws to an end, other players continue to enter the race for power. Meanwhile, Cade and Teresa are struggling to deal with an unforeseen situation with their foster children.

When Charlie and Joseph arrest a man on his way to a major drug deal, they end up bringing a bigger fight than expected back to the station. Meanwhile, Cade and Teresa continue to deal with the complication in the adoption of their foster children and Bill comes to a big realization about his job as Sheriff, as the window on his term continues to close.

Charlie, Joseph and Carter investigate a case that becomes more complicated at every turn, while Bishop and Cade make a connection to a homicide they never expected. Still suffering flashbacks from the hospital takeover, Paula tries to find closure. Meanwhile, Bill's family strives to humanize him to the constituents of Los Angeles County

When informants for the Sherriff's Department start turning up dead all over Los Angeles, everyone has to work together to find the leak in the department. Meanwhile, Teresa and Cade deal with a major setback in the custody battle for their foster children. Also, on the day of Maggie's Quinceanera, Bill gets stuck in a difficult position between work and family in the season finale