RetroHound’s review published on Letterboxd:
Robert Donat has a woman say "Take me home with you" so what's a Canadian bachelor in London going do? However, she acts very odd and paranoid and ends up dead in his apartment. He can't leave because the men who did it are watching the apartment building. What should he do? Of course, ring the police and have them get the men outside! But no, then we wouldn't have a movie. Instead, he sneaks out and tries to meet her contact himself even though he knows nothing. And the contact is way up in Scotland. The dead woman is found in his apartment and he's missing, so the police assume he has something to do with her death. Wouldn't you? He has to get off a train in a hurry and I guess walk the rest of the way. When he gets there, the contact is a bad guy! Well it goes downhill from there, except for meeting Madeline Carroll, who acts like a normal person would, which is a relief from all the other contrivances. But then she overhears the bad guys and believes him. Eventually he gets the handcuffs off.
A lot of Hitchcock's tropes appear here, secret societies, innocent man on the run, respectable citizens with nasty lives, being trapped/pursued in a theater(theatre) while a performance is going on, etc. It was very interesting in that way. I liked it more than my review might indicate, if you just go with it there's a lot of tension.