Mitchell Thompson is the parachuted in American actor,who plays a scientist trying to uncover a spy ring.On the basis of his performance in this film it is little surprise that he found his true place in television.John Loder,once incredibly the husband of Hedy Lamaar,plays the police inspector in his usual wooden manner.This was his penultimate appearance in a British film.Also featured are veteran actors Henry Oscar and John Stuart.The film was clearly influenced by the Burgess/Maclain case to which Loder actually refers.The film is as exciting as a cold cup of tea.Interesting to see London in the 1950s,still showing the effects of the blitz and very much down at heels.