A GI in Vietnam saves his buddy's life, but in the process is shot in the head. The injury results in brain damage to the point where he basically has a child's brain in a (very large) man's body. When they get out of the army the two open up a bar together, but some local gangsters make things tough for them after they refuse to take part in brutal "cage" matches where fighters battle to the point of serious injury and/or death.

Four losers borrow money from gangsters to bet on a "sure thing", but lose. The gangsters go after them to get their money.

"Bags" the boxer (Tim Conway) and his manager, Shake (Don Knotts), are quite a pair: One is a dim bulb, and the other has a mean streak. Times are tough and they must save their gym, so they line up some money making fights. But when Bags and Shake discover that the bouts have been rigged, they end up with their backs to the wall and must fight back -- literally.