The events of the four books take place roughly over ten months; with the events of each book occurring during a traditional British school holiday period. Effectively, each book reflects a season: "The Steps up The Chimney" takes place during the winter and over the Christmas holiday; "The Door in the Tree" takes place in spring, during the Easter holiday; "The Tunnel behind the Waterfall" takes place during the long summer holiday; "The Bridge in the Clouds" takes place during the shorter autumn half-term. During these holidays, the children's parents are carrying out humanitarian work in the Third World, so the children stay with their uncle Jack and his partner Phoebe.