Lupin and Jigen go looking for a treasure in an old castle, converted into an hotel, which is said to be haunted by a ghost. Here, Lupin must face an aged woman thief and her two sons, but is helped by a little girl, Carla, who claims to be the owner's daughter. At the end, Lupin manages to find the treasure room, but in the meantime he finds out that Carla herself was the ghost (in the treasure room there are also her bones); however, since someone has been able to find the treasure, she can finally rest in peace.