Nancy and her friends are to travel to New Orleans during the Mardi Gras celebration and explore a mystery surrounding an old river showboat. The boat River Princess ran aground during a storm and has been abandoned since then. The goal is to restore it before Mardi Gras so that a Southern belle can host her engagement party on
it.Strange things have been happening on the boat, leading many to believe that it is haunted. Nancy and her friends delve into the mystery, despite the apparent dangers.