Gumby has a surprise for Minga, Prickle, Goo, and Pokey: a picnic at the very edge of the Grand Canyon. Afterward, they decide to explore an old mine. The mine's caretaker isn't pleased with the idea, but for no reason at all he warms up to them and lets them in. They go 2000 feet down to take the grand tour of the hole in the ground. Unfortunately, there's an earthquake and subsequent cave-in, trapping Minga behind feet of solid rock!