Amateur fighter and all-around bully Muggs McGinniss (Leo Gorcey) tries to cheat in a pool game with hustler Harry Wycoff (Gabriel Dell). He is thwarted by his own friend Danny Lyons (Bobby Jordan), who has some strong ideas about right and wrong and wants to keep his friend honest. Muggs has to knock Wycoff down with his fists to avoid paying off, and promises to get even with Danny and criticizing him as a coward, without the "killer instinct" it takes to win, in boxing or anything else, as far as Muggs is concerned. In revenge for his pummeling, Wycoff, who works for a local bookmaker, arranges to have Muggs kidnapped ahead of the amateur boxing match in which he's supposed to fight. Danny goes into the ring in his place and wins, but Muggs is convinced that Danny arranged the kidnapping. They clash over and over throughout the movie, in an amateur dance contest and as rivals for a job at a local garage, and over Danny's wish to marry Muggs' sister, and then Muggs finds out that he was all wrong -- that Danny had nothing to do with thekidnapping. But by then he's jealous of Danny, and continues riding him mercilessly, and Danny can't fight back because he's promised his mother never to fight in the street like a common hooligan. Muggs gets even more fierce in his resentment when Danny joins the army showing himself to be more of a man than Muggs and becoming a hero to the neighborhood in the bargain. Finally, Danny realizes that if Muggs is ever to grow up, someone is going to have to stand up to him. The two agree to settle their differences with their fists.