A railroad worker accepts a colleague's offer to stay in his home, but when his friend is called out one night to stop a runaway train, he makes a play for the man's wife.

Dave Tolliver, tower signalman on a mountain railroad, takes in his relief man, Joe Standish, as a boarder. For a time, Joe seems like an entertaining guest, but during a storm, he becomes drunk and makes advances to Dave's wife, Sally. Although little Sonny Tolliver warns his father of Sally's predicament, Dave is compelled to stay on the job when a runaway freight endangers a passenger train. He ditches the runaway and saves the express, while Sally successfully defends herself by shooting Standish.