On a planet in a distant galaxy: the power-hungry dwarf creature Leprechaun is holding a beautiful princess captive. Marriage to her and his gold will secure his rule over the universe. He reckons that a spaceship has already landed with a company of marines to thwart his plans. After her rescue, the princess is transferred aboard the spaceship of the obscure Dr. Mittenhand. He is a combination of human and computer and wants to use her alien-rejuvenating DNA gene to regain his former human body. But then the tricky Leprechaun suddenly appears on board and manipulates Dr. Mittenhand's DNA mixture. This instantly transforms him into a gigantic, blood-sucking creature. A murderous battle begins for the crew against this monster, the clever Leprechaun and the spaceship's self-destruct timer - a deadly countdown begins!