Gemstone, the Mermaid's Scale, appears in a secret, underground auction. The queen of the underworld coerces Lupin into stealing the rock for her. Quickly discovering not only that the stone is a forgery, but that the real Mermaid's Scale is part of an unsolved riddle that leads to transcending mortality!

In this Japanese drama, a dry goods merchant's daughter is surprised to discover that she has a twin sister. In rural Japan it was thought that twins bring bad luck, so the sister was abandoned at birth. Later her parents tell her that her sister was kidnapped. The woman doesn't believe this and when she eventually meets her twin, both women are involved in love affairs. The merchant's daughter is seeing an educated fellow. Trouble ensues when she begins suspecting that he may be more interested in her sister.