Michael Young is a brilliant young history student whose life is changed when he meets Leo Zuckerman, an ageing physicist with a theory that can change worlds. Together they realise that they have the power to alter history and eradicate a great evil. But tinkering with timelines is more dangerous than they can imagine and nothing - past, present or future - will ever be the same again. ''The tensions and resolutions are intrinsically comic, made still more enjoyable by [Fry''s] sinuous invention and cleverness at caricature'' Spectator ''Sprightly and entertaining'' Telegraph