Author Honobu Yonezawa plays the conventions of the closed circle mystery to the hilt, while also paying homage to some of the classics of the genre, such as Agatha Christie's And Then There Were None?for example, by inserting the Native American doll of that work as a prop in this story set in contemporary Japan.
"Subjects wanted for a humanities-related experiment. Will be held in confinement and observed 24-7 for a period of one week," announces a help-wanted ad; the stated wage?could it be a misprint??is 112,000 yen (about $1,120) per hour. Eight men and four women are lured by the lucrative compensation to sign up. They are taken to a remote location and confined in the basement of a highly secure building. There are no signs of anyone else around, and there appears to be no route for escape. In the afternoon of the first day, a voice piped in by speaker announces that the experiment has been designed to study the dynamics of hatred, anger, and mistrust among the participants, and informs them that those who kill someone else, those who are killed, those who finger a killer, and those who assist anyone who fingers a killer will all receive a substantial bump in pay. In essence, the sponsor has set up a game of "murder and detection" among the subjects, and intends to sit back and watch for enjoyment. Each of the private rooms to which the subjects are assigned has been furnished not only with a detailed rulebook but also with the necessary means for poisoning, bludgeoning, strangling, etc.?i.e., for murdering by whatever method the occupant might choose. The game will end when seven days have passed, when someone finds the hidden passageway and makes a successful escape, or when only two survivors remain. If they can simply survive the seven days, each of the twelve subjects will take home nearly 19,000,000 yen (about $190,000).
But on the morning of the third day the first victim?a male?is found shot with a gun, and by the sixth day, six of the 12 subjects have been killed?five males and one female. The perpetrator remains unidentified. The deep mutual suspicion with which the survivors regard each other may be purely conventional, but the author shows his cleverness and originality in numerous other ways. The point-of-view character is Rikuhiko Yuki, a college student who signed on in hopes of earning enough to buy a used car. Yuki belongs to a mystery lover's club and is a huge mystery buff. Though initially terrified for his life, he reins in his fears and begins calmly reasoning his way through the evidence, leading readers to think he will be the one to solve the crimes. But his brilliant deductions earn him the antipathy of the others, causing them to vote him the perpetrator and lock him up in the prison cell. Which leaves readers to wonder: who is the true culprit, still free to kill?
A feature film based on the book and directed by Hideo ("The Ring") Nakata was released in Japan in 2010.