Seven college students, all members of a mystery club, organize a week-long excursion to Tsunojima Island, situated off the coast of Japan. This is where the owner, his wife, and the housekeepers were brutally killed six months ago, and the case is still unsolved. Upon their arrival, the students start to suspect that one among them is plotting to murder the rest of the group individually. The question that lingers is - who among them is the perpetrator?