It's Christmas time and the Murtaugh family is headed to Hawaii. However, Murtaugh's vacation is put on hold when he and Riggs are called to a homicide and the victim is an old friend.
Riggs and Murtaugh are drawn into a fatal world of conspiracy theories. Meanwhile, Riggs' relationship with Molly evolves and Murtaugh and Trish attempt to get Harper into a fancy pre-school .