Rosie must get Augustus back. He may be a big, sloppy dog and her grandpa Harry says he can't live in the flat, but he forgets how much you can love a dog.
He is the true-blue friend of Rosie's soul and she will do anything to find him.
She doesn't need any help, especially not from Philippe, the new boy downstairs, because he is useless and looks like a puppy about to be kicked.
She'll have to face Swanson, who never talks to anyone and always knows when you've stolen her apples.
Rosie is about to embark on an incredible adventure . . .