The Mermaid Hotel is the BEST place to live if you're an adventurer. There are rooms to explore and secrets just waiting to be discovered... Mabel likes to keep an eye on all the comings and goings at the hotel. When a mysterious old lady moves in, Mabel vows to watch her every move. Because this guest, Mabel decides, is a SUPERVILLAIN. But as an unlikely friendship grows between the pair, their fantastical exploits take them well beyond the corridors of their seaside home.