Sabotage

A citywide blackout hits London after sand is placed in the generator bearings. Patrons at Karl Verloc's cinema demand their money back, and Verloc slips into the back rooms. As the refunds are about to be disbursed, the lights abruptly come back on.

The next day Verloc meets with his contact, part of a clandestine terrorist cell planning attacks in London. The motive remains unclear, but the group assigns Verloc tasks. The contact hints at explosive action to come.

The contact instructs Verloc to place a parcel at Piccadilly Circus tube station during the Lord Mayor's Show. The plan is framed as fireworks, but the undercurrent is to enable a bombing. Verloc is uneasy about the violence involved.

Verloc is given the address of a bird shop owner who makes bombs. The bomb-maker agrees to prepare a time bomb to explode at a set time. Verloc's willingness to cooperate grows with the approach of the Saturday deadline.

Scotland Yard suspects Verloc's involvement and plants Detective Sergeant Ted Spencer undercover as a greengrocer's helper beside the cinema. He befriends Verloc's wife and Stevie while keeping their true intentions hidden. The police grow increasingly convinced Verloc is connected to the plot.

Spencer is invited to a meal at Simpson's with Mrs. Verloc and Stevie and begins to feel protective toward them. He remains unsure about Mrs. Verloc's innocence, but the interactions tempt him to trust her more. The tension between suspicion and sympathy grows.

Verloc goes to the bird shop and learns the bomb-maker will set a time bomb to explode at 1:45 pm on Saturday. The plan crystallizes, with Verloc still reluctant to carry out violence himself. He weighs how far he will go for the cause.

That night, the terrorist cell gathers in Verloc's living room above the cinema. Spencer tries to eavesdrop but is spotted and recognized. The gathering disperses in haste as suspicion falls on them.

The next day Verloc receives a package containing two caged canaries for Stevie, along with the bomb. Spencer confronts Mrs. Verloc about the police suspicions. The web of deceit tightens around Verloc and his household.

Verloc asks Stevie to deliver a film canister to another cinema and deposit a second package in the cloakroom at Piccadilly Circus station by 1:30 pm. The assignment appears routine, but it hides a deadly time bomb. Stevie unknowingly becomes the carrier of catastrophe.

Stevie is delayed by the Lord Mayor's Show procession and other obstacles. He boards a bus to Piccadilly Circus carrying the bomb, which explodes at 1:45 pm, killing Stevie and others. The bombing shocks London and foreshadows the tragedy to come.

After Stevie's death, Verloc confesses to his wife, blaming Scotland Yard and Spencer. He moves toward Sylvia with a knife and stabs himself, dying at the moment of confession. Spencer arrives to arrest him but finds him already dead.

Spencer arrives to arrest Verloc but discovers he is dead. He urges Mrs. Verloc not to admit stabbing, fearing she would not be believed. He resolves to help her leave the country if possible.

The bomb-maker returns to Verloc's flat to retrieve the birdcage, but the police are already following him. He detonates a bomb he carries, killing himself and destroying Verloc's body. The immediate danger to the police is revealed as foiled.

The police superintendent is unsure whether Mrs. Verloc spoke before or after the explosion. Ted and Mrs. Verloc walk away through the street crowd, leaving the case unresolved. The tragedy tightens the mood of London as the episode closes.