Weirdo Halloween

On October 30, brother and sister Chris and Meg rescue a young child in a costume from a gang of bullies, only to discover the "kid" is really Weirdo, a smelly alien with a lot of disgusting habits, who promptly swears allegiance to them. On October 31, Weirdo's people invade Earth, and the twins find their souvenir from HorrorLand may be the only thing that can save or harm them! In the second part of the story, Chris and Meg return to HorrorLand and meet the protagonists of the previous three books, and are sent on a mysterious mission by Jonathan Chiller.