Carefully planned, four outlaws met in a saloon in Boise City, Idaho during May, 1865. Leading the "gang” was a man named Brockie Jack who had recently broke out of a jail in Oregon and had been hiding out on a nearby ranch. The next main member of the group was Big Dave Updyke, who had been elected Ada County Sheriff just a few months previous. Parading as a descent citizen, he was known to have consorted with known felons and was watched closely by the Payette Vigilance Committee. The third member was a man named Willy Whittmore, who was known for his quick temper and deadly aim. The fourth man was a little known player that went by the name of Fred Williams.

On May 31, 1865, the four outlaws left Boise City headed toward the Portneuf Stage Route in eastern Idaho, more than 200 miles away. Making camp at Ross Fork Creek near Fort Hall, the men worked out the details of the hold-up. Fred Williams was sent to Virginia City, Montana to gain information about the gold shipments. Once he was sure that the stage line would be carrying the precious cargo, he was to purchase a ticket and ride along as a passenger.

In the meantime, the other three bandits traveled south along the stage road, looking for the perfect place for the hold-up. A few miles south of present-day Pocatello, Idaho, the trio found a narrow canyon that was heavily timbered, rocky, and filled with brush. Determining that the location provided everything that was needed, the bandits began to work out the details of the robbery. They soon gathered a number of large boulders that would be utilized to block the stage road, hiding them out of sight until they were needed. Additionally, they decided that Willy Whittmore, armed with a new Henry repeating rifle, was to shoot the lead horses if the driver found a way around the roadblock.

With the details worked out, the three bandits returned to Ross Fork Creek to wait for their accomplice, Fred Williams. It would be nearly two weeks before they received any word.

On July 21, 1865, the stagecoach left Virginia City with seasoned driver, Charlie Parks, and seven passengers, including one calling himself Fred Williams.

Crossing the Ruby Mountains, the stage spent its first night at the Corral Station near present-day Dillon, Montana. For the next three days, the stagecoach traveled along the route, where the Union Pacific Railroad would later be built, to Pocatello.