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.

Reparto

George O'Brien

Tim 'Hard Rock' Harrigan

Irene Hervey

'Andy' Anderson

Fred Kohler

Black Jack Riley

Dean Benton

Michael McGinnis

Frank Rice

McClintock, Superindendant