The three Emerson brothers (Sam, Jake, and Kal) came to the base of Thunder Mountain looking for gold because of a legend told them by an old Indian. And strike gold they did -- a rich lode that could be worth millions. Sam keeps guard on their claim while Jake heads to Boise to obtain financial backing for their operation and Kal goes to the nearby town of Salmon to purchase supplies. In town, Kal comes to the rescue of a young lady being bothered by an over-demanding Cliff Bordon. The young lady in question is Sydney Blair, who came west with her father looking for a new start. Kal invites them to go with him back to Thunder Mountain. When they get there, Kal discovers that a small community had sprung up in the few weeks he had been gone. Word of their discovery had evidently got out. Of his brother Sam, there is no trace and Kal is told that a man named Rand Leavitt had laid stake to the claim.
Thunder Mountain (both the novel and the comic book adaptation) is a classic tale of gold, greed, and vengeance. Grey based his story on historical fact. Yes, there is a Thunder Mountain, Idaho, and around 1894 three brothers, Lew, Ben, and Dan Caswell came there in search of gold. Their adventures, as told to Grey by local guide Elmer Keith, formed the kernel of Grey's book.