When Detective Bailey's sister, Jess, runs into trouble with the law, Bailey must decide how far she's willing to go to protect her family. Meanwhile, with Trish away on a company retreat, Murtaugh is left to help Riana navigate boy problems, and Riggs deals with the fallout of a night of heavy drinking.

After the city's gun buy-back program is robbed, the team is on a hunt for those responsible. Meanwhile, Murtaugh walks on thin ice with Trish, Riggs finds an unlikely friend in Ruthie, and Captain Avery is reunited with a college "frenemy" who has key information about the case.