The US Army has decided to modernize its cavalry, so Colonel James E. Devers (commanding the 36th Division) is ordered by a general to convert a horse unit to motorcycles, but his men are easily outclassed as riders by a pack of rowdies, especially Grady Westfall; when he is arrested risking a long jail term, he's given one way out: enlisting as Corporal, assigned as driving instructor. Unit commander Captain Jack Hassler reviles his unorthodox boyish methods as undermining discipline and tradition, not to mention flirting with the Colonels daughter Beryl Ann, but he's needed, especially when he unit is ordered to prepare in two weeks for a secret mission to free nuclear scientist Dr. Tate and his daughter Claire from captivity in a castle in general Franco's fascist Spain that can't be reached by parachutists, under cover of a motorcycling festival in nearby Bilbao. Grady didn't want to participate, but when he realizes they're just not up to it, he comes along, and finds the mission...