A group of injured officers escape from a military hospital and devise a plan to shell a Nazi cannon. They proceed across the English Channel in a stolen boat, sneak into France, and dismantle the weapon. Trying to bicycle back to safety disguised as Germans, they are captured by members of the French Resistance, who naturally mistake them for the enemy. Finally, they are released, hailed as heroes, and sent on another mission by British intelligence. This comedy works in spots, especially in its slapstick routines.