Colonel Sangster and his gang are smuggling art treasures and industrial secrets out of the country and selling them on to foreign powers. Tibbs, Sangster's pilot, uses a complicated method of getting the crates with the illegal cargo past customs by taking them out of the country having misdeclared them on paper-work and, having been recalled to rectify the mistake, substituting an innocent cargo which is passed by Customs. Doyle goes undercover to infiltrate the gang.
—don @ minifie-1