Elizabeth, Jeremy, and Harry Martin are three children who have had up to the edge with their mother, a nagging workaholic. Soon, they meet a mysterious gardener named Mrs. Cavour, who tells the siblings of an ancient spell that will make their mother disappear. After saying the incantation one night, the next morning, their mother has disappeared along with their memories of her. Mrs. Cavour tells the children of a place in town called the Mommy Market, where they have about every kind of mother one can think of. The Mommy Market has a policy, however, that one receives three tokens to take one of the mothers home, and if the children do not find a suitable mother by their third token, they could not return. Unfortunately for the children, the mothers they pick, a snappy French woman, a nature-hiker, and a circus performer, do not sit well with the kids, now feeling lost without a guardian to look after them. They want their own mother and try to remember something about her to break the spell.