Number Four is an alien from the planet Lorien, which was destroyed by another evil race, the Mogadorians, whose sole purpose is planetary extinction. Number Four wasn't the sole survivor, as there were eight others, along with their guardians, who escaped the planet's destruction. These nine remnants are destined to use their inner powers to defeat these evil intergalactic terrors, but they must survive long enough to master them. The aliens seek out the survivors, one by one, in order of their number. Numbers one through three have been killed. Number Four is next.