For as long as crime boss Albert Mendoza (Everett Sloane) has been running a notorious ring of hired hit men, District Attorney Martin Ferguson (Humphrey Bogart) has been hunting him down. But Ferguson cuts a deal with Mendoza's henchman Joe Rico (Ted De Corsia), and the mob boss is finally arrested. However, Rico dies mysteriously before he can testify against Mendoza.

As a penalty for fighting fellow classmates days before graduating from West Point, J.E.B. Stuart, George Armstrong Custer and four friends are assigned to the 2nd Cavalry, stationed at Fort Leavenworth. While there they aid in the capture and execution of the abolitionist, John Brown following the Battle of Harper’s Ferry.