George Caldwell, un editor de libros, durante un viaje en tren de Los Ángeles a Chicago, conoce a la secretaria de un profesor y escritor de arte que acaba siendo asesinado. Todo parece indicar que el autor del crimen es Roger Deverau quien intentará eliminar a Caldwell, que ha sido testigo de la desaparición del profesor.

Suspicious husband follows his wife and her male boss on their business trip.

A man and a woman, each with a stable marriage of their own, meet in the wagon compartment. The short encounter of two strangers causes restlessness within their personal views about the world, implying possible romance. Once the train reaches its destination, they go apart without a single word spoken, and return to their world of security.