This VERY British 'thriller', in the worst meaning of the word, is honestly one of the most BORING movies I've ever seen. The 'atmosphere' for the meager plot consists merely of some known ingredients for a good murder mystery, like an old house, a foggy night, and a mysterious masked man called 'The Shadow', a notorious blackmailer who's driven quite some prominent people to suicide for the most ridiculous reasons of 'honor' and 'fear of scandal'.
Those who manage to sit through the whole film (and its running time is only 70 minutes, anyway!) without falling asleep, will witness some very poor attempts to bring in some humor, and even poorer attempts to bring in some kind of action or suspense; the acting is awful (even by Elizabeth Allan, who a year later would deliver a wonderful performance in "Mark of the Vampire"), the direction as stiff as the dialogs... And to imagine that at the very same time, in the very same country, the great Alfred Hitchcock was already developing a new kind of thriller that would make even American audiences shudder...!