An authoritarian rancher, Barbara Stanwyck, who rules an Arizona county with her private posse of hired guns. When a new marshall arrives to set things straight, the cattle queen finds herself falling, brutally for the avowedly non-violent lawman. Both have itchy-fingered brothers, a female gunman enters the picture, and things go desperately wrong.

The wife of marshal Matt Morgan is raped and murdered. The killers leave behind a distinctive saddle, that Morgan recognises as belonging to his old friend Craig Belden, now cattle baron in the town of Gun Hill. Belden is sympathetic, until it transpires that one of the murderers is his own son Rick, whom he refuses to hand over. Morgan is determined to capture Rick and take him away by the 9.00 train; but he is trapped in the town alone, with Belden and all his men now looking to kill him.