"Mabel likes to keep an eye on all the comings and goings at the Mermaid Hotel. When a mysterious old lady moves in, with a jewel filled trunk and a beady-eyed pet tortoise, Mabel vows to watch her every move. Because this guest, Mabel decides, is a supervillain. But even supervillains have a soft side, and as unlikely friendship grows between the pair, their fantastical exploits take them well beyond the corridors of their hotel home"--Jacket flap.