A friendship develops between Bill Denny (George Segal) and Charlie Waters (Elliott Gould) over their mutual love of gambling. Charlie is a wisecracking joker and experienced gambler constantly looking for the next score. Initially, Bill is not as committed a gambler (he works at a magazine during the day), but he is well on his way. The two bond when they are wrongfully accused of colluding at a casino’s poker table by an irate fellow player.
As the two men hang out more, Bill becomes more addicted to the gambling lifestyle. He goes into debt to Sparkie (Joseph Walsh), his bookie. Bill hocks possessions to fund a trip to Reno, where he and Charlie pool their money to stake Bill in a poker game (where one of the players is former world champion Amarillo Slim, portraying himself). Bill wins $18,000 and becomes convinced he is on a hot streak. He plays blackjack, then roulette and finally craps, winning more and more money.
But something happens at the craps table. When he finally stops, Bill is drained, almost apathetic. After they split their winnings ($82,000), he tells Charlie he is quitting and going home. Charlie does not understand it, but sees that his friend means what he says, so they go their separate ways.