The president of the railroad wants to see Casey urgently after a train wreck occurred during a railway strike. He is instructed to take a United States Marshall and a star witness non stop to Denver. During a run through a tunnel, the Marshall is shot. The witness explains she is aware of a gang, the Worker's 7 who caused the wreck, and they may be after her. A desperate race against time develops as Casey tries to find a bomb hidden somewhere on the train while keeping to his tight schedule
