When wealthy pharmaceutical magnate Sahei Inugami dies in 1949, his family gathers for the reading of his will, only to discover that his enormous fortune has been left under extraordinary conditions. Detective Kosuke Kindaichi is drawn into the inheritance dispute when the family begins to turn against itself and a series of murders follows. As Kindaichi investigates the Inugami family's tangled relationships and long-hidden secrets, the mysterious return of Sahei's grandson Sukekiyo—whose face is concealed behind a white mask after suffering severe injuries during the war—adds another layer to the deadly mystery.