The duo sets out to unlock a case about a veteran hitman who Murtaugh has followed for years. Meanwhile, Riggs struggles to find a connection with his father, Murtaugh scares Riana with his overprotective driving lessons, and the team finds themselves wedged in a dangerous incident that tests their trust.
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.