It's Christmas time and the Murtaugh family is headed to Hawaii. Murtaugh's vacation is put on hold when he and Riggs are called to a homicide and the victim is an old friend. Riggs gets a surprise phone call from a relative just in time for Christmas.

The squad is on high alert after an apparent threat is made on Riggs' life. With Murtaugh taking on more responsibility at work, he and Riggs have to deal with their changing relationship. Trish gets caught up in some trouble. Molly asks Riggs to make a big decision about their future.

Murtaugh turns to Cole's former mentor for help on a high-stakes cartel case. Murtaugh and Trish meet Natalie and Maya for the first time. Tensions mount between Bailey and 'The Gute' as the new partners begin to work together.