As the movie opens, a young ne'er-do-well named Lightfoot (Jeff Bridges) is stealing a car, and independently, an assassin is preparing to kill a minister at his pulpit (John "Thunderbolt" Doherty, played by Clint Eastwood). Thunderbolt escapes on foot and Lightfoot inadvertently rescues him by running over his pursuer. It emerges that Thunderbolt is a veteran bank robber who had been hiding under the guise of a clergyman following a successful looting of an armored car company.
The money from that heist was never recovered; only Thunderbolt knows where it was hidden, his previous partners assume that he stole it (and hence are trying to kill him). When they check, Thunderbolt and Lightfoot discover that the old one-room schoolhouse in which the money had been hidden had subsequently been replaced by a modern structure, and they conclude the cash was accidentally destroyed.
Thunderbolt and Lightfoot eventually unite forces with their remaining pursuers, Eddie Goody (Geoffrey Lewis) and the menacing Red Leary (George Kennedy). The mastermind of the old gang had died of a heart attack, and their electronics expert died when Lightfoot ran over him with his car near the beginning of the movie, but Lightfoot nonetheless convinces the group to rob again the same company they had robbed the last time, using a variation on their original plan.
The team succeeds in getting the cash, with Thunderbolt blowing a hole in the wall of the safe using a military cannon. The police are soon on their trail. Goody is shot by the police and thrown out of the car by Leary, and Leary then beats both Thunderbolt and (brutally) Lightfoot, before stealing their car and the loot. He is soon killed as well. Thunderbolt and the now badly injured Lightfoot escape. They stumble across the one-room-schoolhouse in which the loot from the previous heist had been hidden; the Montana Department of Highways had moved it to a new location to serve as a tourist site. The pair recover the money and Thunderbolt buys a white Cadillac convertible - the car Lightfoot had earlier expressed a wish to own - before Lightfoot dies of his injuries.
According to Steven Bach's book Final Cut, the film did respectable box office business, and the studio turned a profit, but Clint Eastwood vowed never to work with the movie's distributor United Artists again due to what he felt was poor promotion of it.