If Jane and Mark and Katharine and Martha had stopped to think, they might have ordered magic by the pound, or by the day, but a lakeful of magic causes extraordinary and unexpected events. By the end of vacation, with an unwilling sly old turtle, and Ali Baba's forty thieves, they help stepfather Mr. Smith save his failing bookstore in a most surprising way.
When the ancient toy soldier comes alive, the Old One grants Roger's wish to adventure in "yeomanly" Sherwood Forest. Will Roger earn his second wish, to save his father? Need for an operation brings Roger 11 and younger Ann to stay with bossy cousin Eliza and Jack. Can the children convince Ivanhoe to marry Rebecca over Rowena, and conquer the castle - in pjs?
Just when the children thought the magic in the old well was all played out (that is, if it was magic!) and had sworn an oath in blood not to make any more wishes until the well gave them a sign, Gordy—in a reckless moment—told it to get going with its magic, or else! Something certainly did begin to happen then, whether it was magic or not, for a strange, witchlike old woman came to the children's secret house in the wood soon after and led Gordy away. The most unexpected things kept on happening all through that eventful autumn, just the sort of things an unpredictable wishing well might involve them in, from reforming a nearly delinquent juvenile at school, keeping apple trees and romance in bloom, and rescuing a damsel in distress, to helping a new family settle in the community.
Four children wish on a Half Magic coin that gets their mother Alison half-way home, rescued by Mr Smith. Mark's wish zaps them to a desert without island, where half-talking cat Carrie gabbles to a camel. Romantic Katherine battles Launcelot. Eldest Jane rejects siblings for another family. Stubborn youngest, Martha, causes a riot downtown.
"Anything can happen when you have all the time in the world" says the frog-like Natterjack in old relative Mrs Whiton's thyme garden. Cousins Roger, Ann, Eliza and girl-crazy Jack ride for American rebels, bow to Queen Elizabeth I, and even rescue their own parents when they were children.