Texas Ranger Jake Cutter arrests gambler Paul Regret, but soon finds himself teamed with his prisoner in an undercover effort to defeat a band of renegade arms merchants and thieves known as Comancheros.

San Francisco Police Inspector 'Dirty' Harry Callahan and his new partner, Early Smith have been temporarily reassigned from Homicide to Stakeout Duty. Meanwhile, those of the city's criminals who manage to avoid punishment by the courts are nevertheless being killed by unknown assassins. Callahan begins to investigate the murders despite the orders of his superior officer, Lieutenant Briggs. A man has to know his limitations...