Casper emerges from a subway station, following a crowd of scared strangers. He encounters a man saying "see the wonders of the moon for ten cents," and offering a sight through a telescope. Casper scares the man away, then uses the telescope to see the moon. He then flies to the moon for a visit. Casper lands on the moon, disappointed to find no man on the moon. He lies down to nap, then tiny moon men emerge from holes. They capture Casper, lock him in a cage, and tow him to King Luna. The King addresses Casper as a monster and treats him as an enemy. Casper playfully picks him up, only to be placed in the royal dungeon. Then, tree monsters attack. The Moon Men defend their fortified city with flaming missiles. The tree monsters fight back with water, then break through the town walls. Casper escapes his cage, and helps the Moon Men by going underground and tying the trees' root feet together so they can't attack. After the Moon Men win the battle, King Luna knights Casper for the valiant defense of his people.