Watch out! Beware! A mischevious Simon wanders into the Hammonds twins' lives and sparks mischief in the house. Ingeniously using electronics, he creates mayhem with prank spiders, spins stories that the old mill is haunted and talks Jerry into sneaking out after dark to see the 'ghost'. Tables are soon turned when Lou and the girls decide to get their own back on Jerry and Simon for all their pranks. Skippy saves the day as he finds Simon trapped in the haunted house and alerts the others.