At the breaking of the Civil War the garrison of Fort Laramie splits between the sympathezers of the two different factions, but when the fort is attacked by the Sioux, they unite their forces to fight them.

Future “first couple” Ronald Reagan and Nancy Davis made their only joint film appearance in Hellcats of the Navy. Ronnie plays Casey Abbott, commander of a WW2 submarine, while Nancy portrays navy nurse Helen Blair, Abbott’s off-and-on girlfriend. During a delicate mission in which his sub is ordered to retrieve a revolutionary new Japanese mine, Abbott is forced to leave frogman Wes Barton (Harry Lauter) behind to save the rest of his crew. But Abbott’s second-in-command Don Landon (Eduard Franz) is convincing that Abbott’s sacrifice of Barton was due to the fact that the dead man had been amorously pursuing Helen.