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. Meanwhile, Riggs gets a surprise phone call from a relative just in time for Christmas.

When Riggs visits his father-in-law in prison, a walk down memory lane reveals an old secret about his deceased wife. Meanwhile Murtaugh tries to impress Captain Avery, and, united by the death of a mutual friend, Trish and Leo Getz try and solve a murder on their own.