A spaceship approaches third Earth and it sets off all the alarms of the ThunderCats, Mutants and even Mumm-Ra. It contains enough radioactive material to put an end to the ThunderCats. Jackelman takes the recovered materials first and Mumm-Ra takes it from him. The ThunderCats battle Mumm-Ra on top of the Dark Pyramid for the sphere and eventually win, setting the materials to explode safely in space.