While playing in a gravel pit, five siblings--Robert, Anthea, Cyril, Jane and baby Lamb--unearth Psammead, a sand-fairy who has the ability to grant wishes. Unfortunately, the Psammead has been buried so long that his magic has grown rusty, and the children's wishes go humorously awry. When the children wish to be beautiful, their servants think them strangers and throw them out onto the street. When they wish for jewelry for their mother, all the jewelry in Kent appears in their house. The children must ask the Psammead to grant one final wish to set things straight, but in doing so, they may never see their new friend again.