The doorway

Three teenagers -- Wendy, Brainy, and Thumper -- are drawn into another world when they follow directions in an old book that they found in a reputed haunted house. They are met in this world by a little person warning them that they need to follow him. He leads them into an underground town run by a very tall man named Kor. Kor convinces them to accept a mission to destroy a meteor that has hit their planet and is now poisoning it. The teenagers cross a landscape inhabited by giant snakes, giant scorpions with double stingers, and other dangers. They safely cross the land to the meteor where they set a bomb to destroy it. But something goes wrong. The bomb explodes prematurely just as they slip behind stacks of crates. After narrowly escaping death they discover that they have somehow attained super powers. Now they must learn how to use them before they are killed by an emerging army.