 Canadian Mountie Rod Webb (Kirby Grant) has been assigned to the case where three messengers carrying Kenmore Mine payrolls have been robbed and murdered. He travels to the mine on a train with Jane Kenmore (Gail Davis), niece of the mine owner; payroll messenger Brown; an armed guard named Le Clerque (John McGuire) ; and a young mining engineer, Len (Rand Brooks), and his sister Polly (Margaret Field). Someone sneaks chemicals in the stove and, in the confusion, Brown and the conductor are killed and the payroll vanishes. Rod uncovers evidence that Kenmore and his niece, with the help of Le Clerque, have been robbing their own payrolls.