Earth is invaded by the criminal organization known as Makuu, led by Don Horror, who had first destroyed a space colony near Earth. Don Horror wants to dominate the whole universe, and the Earth represents an obstacle that he has to overcome by turning it into a domain for all evil. In response to Makuu's attack, Space Sheriff Gavan of the Galaxy Federal Police is deployed to Earth to defend his mother's home world.

Space Sheriff Gavan тривав 1 сезон. Нових епізодів не заплановано.