Larry Sutton (Randolph Scott) becomes chief engineer at the Ballard radium mine after the mysterious death of the former chief. Asked by the sheriff to assist in the investigation of the death, Larry learns that his own brother-in-law, as well as the nephew (Howard Wilson) and niece (Kathleen Burke) of the mine owner, Jim Ballard (George F. Marion), are all suspects. When Mrs. Ballard (Florence Roberts) returns from a trip and is not allowed to see Jim, Larry takes an active role in the case.