An energy vampire using the name Valencia Alucard is behind the theft of a priceless jewel, and Mr. Franklin Forrester--the curator of the Mount Melania Museum--has called in the "Super Sleuths Seven" to help him solve this mystery. At Alucard Castle, Roxy is attacked and drained of her energy, and the Sleuths trace her energy drain back to a failed experiment scrapped by one of Eden Starling's friends--but the shocking conclusion is that Miss Alucard is not who she appears to be. Even with some help from the true owner of Alucard Castle--Anneliese Benton--can the Super Sleuths Seven trap Valencia during the annual Alucard Monster Ball and expose her scheme once and for all?