Dave Cameron , sheriff of a small mining town and brother of Joan Cameron (Evelyn Finley), is killed when a Nazi gang tries to blow up the mine, which is supplying the U. S. Government with magnesium. Dan Bartlett (Steve Clark), owner of the mine sends for a trio of troubleshooters, Crash Corrigan (Ray Corrigan), Denny More (Dennis Moore) and Alibi Terhune (Max Terhune) to take over for Cameron. Crash is sworn in as the sheriff, and Denny and Alibi, working undercover, get jobs at the mine. William Werner (Budd Buster), head of the Nazi gang, and his wife Katie (Edna Bnnett), run a saloon. Larry Fraser (John Merton),foreman of the mine, is under Werner's influence and is helping him. Alibi, as a ruse, gets himself fired from his mine job, and joins up with Werner and Fraser. Wener tells one of his henchmen to kill Crash, but the plan misfires and Crash is able to identify the henchman as a mine worker. Alibi overhears plans to blow up the repaired mine and tells Crash and Denny, revealing also that Werners and Fraser are planning to leave town after the explosion. But the Range Busters have other plans for the Nazi rats. .