After unstable former circus performer Dublin O'Malley (Sean McClory) escapes from a mental institution, he goes after Clyde Beatty (Clyde Beatty), the animal trainer whom O'Malley blames for his fate. He is also obsessed with Valerie (Marian Carr), a trapeze performer and old flame. When O'Malley arrives, dangerous accidents start happening around the circus, and manager Frank Wallace (Pat O'Brien) calls for help from mystery writer Mickey Spillane (Mickey Spillane).