When Professor Marsh disappears while searching for the lost city of Lukachukai, his daughter enlists the help of the Three Mesquiteers.

After Jim Blake saves Harve Tarlton's life, they become partners in a gold mining claim. After a while Harve reverts to his outlaw way of life. Everyone but Jim seems to know that Harve is bad but Jim merely thinks he needs a chance to go straight. But Jim's wife Helen has a plan to expose Harve as the outlaw he is.

A rodeo singer funds a little girl's operation with a show, on television.