Frankie Dane (John Cassavetes) is the leader of the hornets, a local street gang that has had its share of rumbles and other trouble with the police. When one of his members is fingered to the police by a neighbor (Malcolm Atterbury) for having a gun, Frankie vows revenge, and when the same man humiliates him in public, he decides it's got to be murder. But only two members of the Hornets, mentally unstable Lou Macklin (Mark Rydell) and would-be full-fledged member "Baby" (Sal Mineo), are willing to go along, and even one of them is shaky -- the rest of the gang draws a line at killing. Social worker Ben Wagner (James Whitmore), who runs the local youth center, has been trying to reach out to the members of the Hornets and sees that something is splitting Frankie and a couple of the others off from the main gang, and is concerned enough to find out what it might be -- especially when Frankie's younger brother, a really nice kid named Richie (Peter J. Votrian), tells him that he thinks Frankie's planning to kill someone. He tries getting help from Frankie's mother (Virginia Gregg), who's too tired from her job to do much more than keep Richie from becoming like his brother, and Mr. Gioia (Will Kuluva), "Baby"'s father, who doesn't understand what went wrong between him and his son. A three-way battle of wills ensues as Frankie tries to hold his plan together and resist Wagner's efforts to intercede -- in the end, several lives are at risk, as Frankie ends up with his knife at the throat of his own brother, fully ready to use it.