Penguin Random House Children's UK

Eight-year-old Jack and his little sister, Annie, are playing in the woods during their summer holiday, when they find a mysterious tree house full of books. But these are no ordinary books . . . And this is no ordinary tree house . . The race is on .

Has it landed in a ghost town? When a gang of nasty horse thieves gallop past, it's not long before Jack and Annie are swept up in another adventure. With their new cowboy friend, Slim, they set out across the prairie to rescue Slim's mare from the horse thieves. But Jack and Annie still have their next riddle to solve.

Whisked away to Africa on this adventure in the tree house, Jack and Annie cannot believe all the wild animals they see. But when their route back to the tree house is blocked by some scary lions they need to come up with a clever plan of escape - and fast!

Jack and Annie are on very thin ice! Morgan Le Fay, the magical librarian, sends the children and the treehouse to the Arctic and tells them she'll send somebody to meet them there. But they're surrounded by ice and snow and there are huskies and polar bears all around them too - will they freeze to death first?