"Smiler" Grogan, a just-released convict jailed for robbery 15 years earlier, escapes police surveillance but crashes his car on California State Route 74. Five motorists stop to help him: Melville Crump, a dentist on a second honeymoon with his wife Monica; Lennie Pike, a furniture mover; Ding Bell and Benjy Benjamin, two friends on their way to Las Vegas; and J. Russell Finch, a seaweed-business owner, traveling with his wife Emmeline and his loud, obnoxious mother-in-law Mrs. Marcus. Just before he dies, Grogan tells them about $350,000 (equivalent to $3.1 million in 2021) buried in Santa Rosita State Park under "a big W". After the group fails to come up with a satisfactory way to split the money, they give up negotiating and begin a mad dash to find it. Unbeknownst to all, Captain Culpeper, chief of detectives of the Santa Rosita Police Department, who had been working the Grogan case for years and hoped to solve it and retire, has everyone tracked.