Kal Emerson (George O'Brien') and his pal Steve Sloan (Dean Benton) have the secret of a gold mine in Thunder Mountain, but no money to finance their prospecting until Kal rescues Sydney Blair (Barbara Fritchie) from the unwelcome advances of a drunken miner. She persuades her father, Samuel Blair (Edward LeSaint), to stake them. When they locate the mine, Kal returns for Sydney and her father. On the trip back, Kal falls in love with Sydney, who pretends to do the same with him because she believes he will soon be a rich man. When they arrive they find that a mining town has sprung up on the site and that Rand Leavitt (Morgan Wallace) is in control of the mine. Sydney and all of Kal's friends turn against him, with the exception of "Nugget" (Frances Grant), a dance hall girl secretly in love with him. Kal is preparing to take Leavit before the miner's court when Steve returns to tell how he had been attacked while on the way to register the claim, but before he can be called as a witness, Steve is killed by Leavitt. Kal warns Leavitt and his henchman Cliff Borden (William Bailey) to leave town. Leavitt kills Borden, and flees town with Kal in pursuit. They are engaged in a battle on Thunder Mountain when there is a rumble and a landslide.