Danny Orlis and the Colorado Challenge — Bernard Palmer

The Davis triplets are upset and discouraged by the news that they have to leave their school and friends to move to Colorado, where Danny Orlis is opening a mission flying school. Danny cheers them up by helping them get jobs at a dude ranch in the hills outside their new city. The triplets make new friends and learn their jobs, and the summer is going better than they expected. But then things take a mysterious turn when an obnoxious coworker goes missing.