Boone Shattuck's brother-in-law had been murdered in a gold robbery and his sister had died of grief. Four men had committed the robbery and Shattuck is determined to hunt them down. He resigns from the Texas Rangers and sets off to find them. He soon discovers that Bass Eccles, the ringleader and the key to finding both the missing gold and the three others, is now in Yuma Prison. Shattuck must find a way to get into the prison and win Eccles' confidence - or die in the process.