The plot revolves around a rivalry between sand-hog "Hard Rock" Harrigan (O'Brien) and his foreman Black Jack Riley. At the center of their conflict is their mutual affection for heroine "Andy" Anderson (Irene Hervey). But when the chips are down and Riley is trapped in a tunnel cave-in, it is Harrigan who comes to the rescue.
George O'Brien
as Tim 'Hard Rock' Harrigan
Irene Hervey
as 'Andy' Anderson
Fred Kohler
as Black Jack Riley
Dean Benton
as Michael McGinnis
Frank Rice
as McClintock, Superindendant
