Spoiler alert from here on.
Hitchcock does provide tension in the pivotal sequence where, because of police surveillance, Homolka is forced to send the young boy out to deliver a package containing a bomb. He emphasizes the importance of getting to his destination by 1:30, knowing the bomb is set to go off at 1:45, but of course the boy doesn't know that and ends up being delayed on his way (comically being dragged into a demonstration by a peddler of toothpaste and shampoo at one point). While we feel the suspense, Hitchcock as a younger director exercises no restraint at all, melodramatically increasing the volume of the music and showing us the time on clocks repeatedly as it gets closer and closer to 1:45.
To Hitchcock's credit (or Joseph Conrad's, the author of the story) the bomb does go off, and it is a little shocking even today. Imagine what the reaction was like in 1936 to have an innocent boy, one moment playing with a puppy on a bus, the next minute gone, along with all of the other passengers. The shock presages other Hitchcock moments, such as the shower scene in Psycho. Unfortunately, in the wake of this, the emotional reaction of the characters doesn't ring true, though it does lead to what I think was the best scene in the movie - the mother thinking her son is running towards her on the street, which for a split second has us somehow believing, as she does, that he's survived.
Watch it for the bomb scene and for Sylvia Sidney, but it's certainly not a classic.
This is a sensational thriller about a couple that run a cinema in London & although she is unaware her husband is plotting to Sabotage London & create terror in the streets with a criminal mastermind.
The film unravels so well & you as viewer journey with the wife to identify her husbands evil motives. The visuals & tension are second to none. It's engaging & perfectly directed, a must see early Hitch .