Murtaugh and Riggs investigate a death that occurs moments before the victim's bet wins a horse race. Leo Getz insists it's a homicide and aids in the investigation. Meanwhile, Murtaugh updates his will, while Riggs struggles to come to terms with his past.
When Texas cop and former Navy SEAL Martin Riggs suffers the loss of his wife and baby, he moves to Los Angeles to start anew. There, he gets partnered with LAPD detective Roger Murtaugh, who, having recently suffered a "minor" heart attack, must avoid any stress in his life.
From the moment the brash and impulsive Riggs meets prudent, by-the-book Murtaugh, it seems as if this partnership is doomed. But after their first case together, both realise this arrangement might just work out after all - if only Riggs doesn't get them killed first.