A retired Atlanta Police Department bomb squad explosives expert, named Howard Payne, attempts to extort money by threatening to kill some people, trapped in a Los Angeles Skyscraper's elevator, with explosives. The city is about to give in when rookie Los Angeles Police Department (L.A.P.D.), Special Weapons and Tactics (S.W.A.T.) officer Jack Traven stops him. Jack and his partner, Detective Harry Temple find Payne and corner him, but he blows himself up instead of surrendering. He is believed to be dead but has actually escaped and again attempts to extort money from the city. This time, he has placed a bomb on a bus that will arm itself once it reaches 50 mph and will explode if it drops below that speed. Payne dares Jack to stop him and tells the whereabouts of where the bus will soon be and the rules of his twisted game. If Jack or the L.A.P.D. attempt and unload any passengers off the bus, Payne will detonate it. Jack attempts to stop the bus before the bomb is armed but it's too late; all he can do now is to keep it going. With Harry attempting to find Payne and Jack running out of freeway and gas - this is one bus ride no one wants to miss.