The Decagon House murders

Seven students from the Kyoto University mystery club sail out to Tsunojima, a remote island. Six months earlier a fire there killed the owner's family and servants. The students lodge in the Decagon House, a ten-sided summer house, and soon a killer begins to pick them off one by one.

The students go by pen names taken from famous crime writers, including Ellery, Poe and Carr. They argue over the conventions of detective fiction even as the danger closes in, so the genre itself becomes part of the talk around the dead.

On the mainland, two other club members receive anonymous letters that accuse several people of the island murders. Kawaminami, a former member of the club, investigates who sent them and why.

The book is a fair-play puzzle mystery in the Japanese honkaku and shin honkaku tradition, built as a homage to Agatha Christie's And Then There Were None. Yukito Ayatsuji published it in 1987, and it opens the Decagon House series. Ho-Ling Wong's English translation appeared from Locked Room International in 2015, with a Pushkin Press reissue in 2020.

The two threads, the island and the mainland, run side by side, and the letters raise the question of who knows what happened on Tsunojima.