The lakeside at Lake Yamanaka is covered with snow. In the vacation house in such a quiet area owned by the chairman of Watsuji Seiyaku, one of the leading pharmaceutical companies in Japan, the tragedy suddenly breaks out. ”I have killed my granduncle!!” says Mako, who is loved by everybody in the Watsuji family. She has stabbed her granduncle, Yohei, to death. Soon after the domestic homicide, the entire family joining together in an attempt to make it look like a crime committed by somebody outside the family, begins to engage in imitative deception…