The Mystery of the Black Hole Mine, Book 7, D.J. Dillon Adventure Series

In exploring the mountains around Stoney Ridge, D.J. Dillon and friend Alfred accidentally discover a long-abandoned gold mine. D.J. picks up two gold nuggets which he believes came from the mine. He believes that there may be more of them inside the mine which is dangerous to enter. A mysterious man threatens the boys and warns them to stay away from the area. Instead of being frightened off, D.J. is convinced that the man is trying to jump the claim to keep the gold for himself. D.J. develops gold fever, and determines to explore the mine in spite of the dangers. He knows that the old mine is unstable and likely to collapse, and that deadly undetected methane gas in the mine can kill a person. D.J. also risks angering the claim jumper, but D.J. enters the shaft alone. That forces him into a horrible situation. In this seventh book, D.J. learns a hard lesson about selfishness and greed.