Mystery Junction

A middle-aged Miss Owens recognises mystery writer Larry Gordon from a photograph on the cover of one of his books as they share a train carriage. She gushes about his novels and asks how he comes up with ideas for his stories. He agrees to tell her, setting up their conversation as the frame for what follows.

Suddenly they hear a scream and discover a train door has been opened, with snow blown into the carriage. Gordon and Miss Owens move through the carriage to check the other passengers and learn what might be happening. The mood shifts from casual chat to a tense mystery aboard the moving train.

They confront Steve Harding, who is handcuffed to Police Officer Peterson, who has a gun. Harding is to appear in court the next day for the murder of a young woman. The other passengers—a broker, an engineer, a woman, and a young man—are connected to Harding in various ways, pointing to a web of motives.

The guard has been assaulted and knocked out by an assailant who stole his uniform coat. Two female stowaways, actresses out of work and short of money, are found hiding in the guard's van. Their presence widens the circle of suspects and deepens the danger on board.

With another police escort missing, the passengers conclude the scream most likely came from Harding, who was thrown from the train by an accomplice. The mystery tightens as it becomes clear someone else is pulling the strings behind the murder case. The threat now seems personal and calculated rather than accidental.

All the passengers leave the train at a junction station to take a connecting service, but the new train has been cancelled due to heavy snow. They take shelter in the station waiting room while they wait for options. The cold and isolation amplify the tension of the unfolding drama.

The station's lighting fails, plunging everyone into darkness and allowing Peterson to be shot. Harding is released by his accomplices under cover of the blackout. Their attempt to escape into the snowy night is thwarted by the severe conditions.

Reinforcements arrive, and the full involvement of the other passengers is revealed. The group’s connections to Harding become clearer as the investigation progresses. The tension shifts from curiosity to a race to prevent further harm.

A confrontation culminates in the shooting of Harding. The accomplice who released him is killed in the exchange as well. It is revealed that this killer had accidentally shot Peterson in the darkness while attempting to shoot Harding.

The scene fades back as Gordon finishes his story idea for Miss Owens. The on-train mystery has been resolved, and his tale draws to a close with Harding defeated and the truth laid bare for the reader and listener.