The flint heart is a stone of heart shape, forged in prehistoric times, that changes whoever owns it into a wicked person. The story of the flint heart's ultimate defeat involves multiple trips into fairyland by Charles and Unity, children of one of the heart's victims. Along the way the reader meets lots of fun characters such as the king of fairyland, a talking (and wounded) hot water bottle, and the mysterious Zagabog. Occasional references to British words and concepts may require some explanation for American readers, but the story is perfectly understandable without such explications. The droll narration makes the story as much fun for adults as for children.