Andrew Morton, best-selling biographer of Tom Cruise, says some Scientologists believe the actor's daughter with Katie Holmes carries the spirit and maybe even the DNA of the sect's founder, L. Ron Hubbard. What else do adherents believe? Despite the fuss around Tom Cruise's manic Scientology video, published here, I didn't have the patience to go through all the background material. (Some of Scientology's critics are even more rabid, and paranoid, than the sect's zealots.) But there's a solution: the South Park's episode, in which one character is briefly lured into the cult, is still up on the web, although Tom Cruise forced the cartoon show's owner Viacom to stop airing the episode on television. In this excerpt, Stan learns Scientology's extraordinary doctrine: that human beings are haunted by the souls of frozen aliens, captured and brainwashed by the evil galactic overlord, Xenu. Bonus fact: Mark Ebner, the Hollywood investigative reporter who first leaked the Tom Cruise video, consulted on this South Park episode. Though it's a cartoon, and mocking in tone, this is a pretty accurate summary of Scientology's far-fetched central narrative. And, blessedly, it's short.