Henry was looking forward to staying with his great uncle.

He was fantastically eccentric - a famous naturalist, his parents said - and within the grounds of his home in the country he had a sort of private zoo. And anyway, Henry hated the idea of the usual family holiday.

He felt stifled and bored by his family and he was pretty sure the feeling was mutual.

He'd be on his own most of the time at his great uncle's, and that suited him just fine.

But Henry wasn't alone. There was that girl, Stella, who alarmed and fascinated him, with her fierce red hair and direct manner. And there was something else, too: something that trod the gravel softly at night and wasn't one of the freely roaming animals; something that howled; something his great uncle was trying to hide from him . . .