An alien invasion prompts a tag-team battle between Godzilla and Anguirus (the planet protectors) and King Ghidorah and new monster Gigan.

An alien invasion prompts a tag-team battle between Godzilla and Anguirus, the planet protectors, and King Ghidorah and the new monster Gigan, a cyborg with scythe-like claws, an abdominal buzz saw, winglike back fins, and pincerlike mandibles.

In this action-packed film, which veers from the sublime to the ridiculous, the cockroachlike aliens—disguised as humans—use Gigan and King Ghidorah as weapons of conquest in their plot to take over a contaminated Earth.