Alfred Hitchcock - Sabotage (1936)

Having recently moved to London from the States, the Verlocs are having troubles making ends meet in owning and operating the Bijou, a movie cinema. What Mrs. Verloc is unaware of is that mild-mannered Mr. Verloc, who she considers the kindest man in the world, has gotten himself involved with terrorists who want to cause general havoc in London. Mr. Verloc's first act to prove his worth, sabotaging the electricity grid to cause a general blackout, doesn't quite have the effect that the terrorists were hoping. As such, they decide on a more explosive second act, Mr. Verloc to play his small part in delivering the bomb to the site, namely Piccadilly Circus. What neither of the Verlocs are aware of is that Ted, the young assistant to the greengrocer located next door to the Bijou, is really undercover Sergeant Ted Spencer of Scotland Yard, he who has been monitoring the Verlocs' movements in suspecting they, he or she are involved with the terrorists, the Yard which has also been monitoring the pet store where the bomb is being manufactured. What happens in this situation is affected by Ted falling for Mrs. Verloc who he comes to believe is innocent of any wrongdoing, and the distracted mind of Stevie, Mrs. Verloc's teenage brother who lives with them.