It's been raining for two long weeks and Georgie's best friend, Sophie, is away on holiday with her family leaving him lonely and bored, when something unexpected happens. Georgie meets Tumph, a pear-shaped, small creature with two short arms, mitton-shaped hands, bright button eyes and seven hairs on his pointed head. He's a letterbug, and he's never met a human before. At first it would seem that they have little in common, but as time goes by, their friendship grows they find that this is far from true...