Who is Madame Badobedah? Mabel sets out to prove that an eccentric new hotel guest is really a supervillain in this witty storybook about an intergenerational friendship.

There's a strange new guest at the Mermaid Hotel -- a very old lady with a growly voice, bags stuffed with jewelry and coins and curiosities, and a beady-eyed pet tortoise. Mabel, whose parents run the hotel, is suspicious. Who is this "Madame Badobedah" (it rhymes with "Oo la la") who has come to stay indefinitely and never has any visitors? To find out, Mabel puts on her spy costume and observes the new guest. Conclusion? She must be a secret supervillain hiding out from the law. The grown-ups think Madame Badobedah is a bit rude -- and sad -- but when she invites "dahlink" Mabel for a cup of forbidden tea and a game of pirates, the two begin a series of imaginary adventures together, and Mabel realizes that first impressions can sometimes be very wrong.