This is a bit tedious. Because of the prospect of nuclear annihilation, a group of scientists and zealots decide we had better have a plan, just in case we cannot stay on the surface. Let's explore under the crust. They are all very dull people, but they must have some expertise because they have developed this burrowing device. No one explains how it runs but it seems to have an endless supply of fuel. It is like a mole (it even looks like a mole) as it burrows through solid rock. Some of the film involves their nutty plan being presented to various corporations and, of course, being turned down. Finally, the playboy son of a financier decides it would be a cool adventure and funds the whole thing. They set out, working their ways through boring scenery and endless dropping into the depths of the earth. There is a device like an EEG that indicates how many miles they are going down. At one point, they leave the water cooler on and all their water drains out (hey Culligan man). Anyway, they come to realize that you can't spend your lives running away (unless you are a knight in Spamalot) and the old earth with its palm trees and oceans and sunlight and fertility ain't so bad after all. It is awfully preachy. Every so often they stop and make uninterrupted speeches about their roles in the world and their abject loneliness. It doesn't work very well.