This story concerns the adventure of two boys, one American and one English, who find themselves by mistake on a vessel bound for New Orleans. Fearing to return to England, they journey to the mining town of Golconda in Utah, which they reach after an adventure with train robbers. In company with a relative of one of the boys they proceed upon a hunting and prospecting expedition, during which they meet with many exciting adventures, but finally succeed in securing the treasure of Mushroom Rock. The story is bound to be of great interest to every boy.