The posse begins their journey on a Smith & Robards train heading west over the Sierra Nevadas. Why they’re on board is up to them. Fate decides to jump their track and the train wrecks. Surviving an attack by Old Ways Apache, the travelers discover the train wrecked because of a massive cave-in, which miraculously leads to a train tunnel going straight under the Sierra Nevadas and most of California.
At the end of the tunnel is a Wasatch railroad digging crew—complete with a wondrous digging machine called the Hellbore. They soon discover that the crew is accompanied by Lacy O’Malley, intrepid reporter for the Tombstone Epitaph. And they meet Dr. Darius Hellstromme himself!
The team bonds with the Wasatch crew when they’re all attacked by ravenous tunnel critters.