Syndi and Mrs. Teller just love the old dollhouse they found at a yard sale, but Marshall and Simon aren't impressed. Still, when they see an interesting doll in a shop window, they make it a present for Syndi. But when Syndi puts the doll into the house, weirdness ensues. And when Marshall sneaks into a real-life house that looks like the dollhouse, he realizes that he's shrinking! What's the connection between all this and the peculiar new girl in school who looks just like Syndi's doll? Marshall has to find out quick, or else move into a dollhouse himself!