In the not-too-distant future, Earth has opened its doors to the universe, and co-exists peacefully with most of the known worlds throughout the galaxy and the many alien species that inhabit them. But like here, there is also crime, and it exists in many forms. The Alienizer syndicate is one of the more powerful and influential crime organizations, and they fund terrorism and chaos as their business through various alien spies, arms dealers, smugglers, and other illegal & dangerous activities. There are also individual criminals out there who indulge themselves in various schemes, cons, and thefts. For those extraterrestrial beings who cannot co-exist peacefully on Earth, there is the special-investigation taskforce known as S.P.D. - Special Police DekaRanger [Detective Rangers]. This intergalactic police force, made up of dedicated humans and aliens, fights to defend the peace & freedom of Earth and its allies.