Stealing a supply truck to break out of a field of a prison in the Midwest United States, Mop and his gang head for the J.S. Diller Dam, intending to blow it up. With Willie the Mop as the gang's leader, the other three are Bummy, SIim, and Snifty; "Snifty volunteered to stay behind and start the riot!" Bummy tells Mop while they drive away. The car pursues the stolen supply truck. Mop throws out dynamite as they cross over a bridge, blowing it up and causing the pursuing police car to crash. Sally's arm is injured in the crash, telling Johnny to maintain the chase.