A huge Comet is headed for earth. As it does not consist of one big piece, but of a cloud of rather small pieces plus a main rock the size of Texas, little impacts are recorded long before the big one is scheduled for collision with earth. Harry S. Stamper and his drill team are selected to land on the main comet as they are the only ones who can work the special drill Harry developed. Their mission is to drill 800 ft. into the comet to place a nuclear explosive device. The explosion of the bomb will break the comet in two, and the two pieces will pass earth on both sides. This task has to be accomplished before a certain ``dead`` line, or the comet parts will not fly by, but hit earth.