The Decagon House Murders

About

Seven members of a university mystery club travel to a remote island where a bizarre murder occurred the previous year. They find a mansion shaped like a decagon — and, inevitably, they begin to die. Meanwhile, on the mainland, a former club member receives a letter from someone who should be dead. The two timelines converge in a revelation that restructures everything the reader thought they understood. Ayatsuji's debut revitalized the honkaku (orthodox) mystery genre in Japan, and the novel's central trick is one of the most satisfying in the form — a fair-play puzzle where every clue is visible and the solution still shocks. The writing is lean, the pacing immaculate, and the body count efficient. The locked-room mystery that launched a genre revival — and the twist that set the standard for everything that followed.