This could have been better as a TV play or radio play or anything but a film.It has a very good cast including that scene stealer,Donald Wolcott,everyone favourite German,Anton Differing,and a pre Dracula Christopher Lee.The film is an old dark house mystery with a Nazi twist.They are going to be told who was the traitor in their midst but the informer is murdered.They don't call the police and decide to find and try the murderer themselves.After another murder the culprit is finally unmasked using one of the oldest tricks known to thriller writers.So it all ends up neatly tied up.Much too much talk and rather statically filmed.