They arrive at the small depot of Cosmos Junction, where a branch line railroad with a temperamental steam-powered streetcar named the "Carolina Cannonball" is operated by Judy Canova and her grandfather.

The three enemy agents ride the streetcar to the other end of the line—the gold mining ghost town of Roaring Gulch—and check into the deserted hotel there, pretending to be uranium prospectors.

Using their detector to get a rough location for the fallen rocket, the enemy agents steal away with the Carolina Cannonball, but its boiler fails, and they abandon it on the middle of the line and walk back to Roaring Gulch.

Unaware of any of the newcomers' true identities, Judy helps the enemy agents track down Mack, thinking him to be a common thief, but encourages them to reconcile.

However, when the brakes fail, the overpowered Carolina Cannonball is unable to stop at the junction, and roars onto the railroad mainline, headed straight for Las Vegas.