A Fiendishly Set Puzzle in The Decagon House Murders (1987) by Yukito Ayatsuji

remote japanese island

‘They are on that fateful island now. Ah well, what’s the worst thing that could happen there?’

Considering this is a novel which openly acknowledges its mirroring of Agatha Christie’s And Then There Were None (1939), these words could definitely fit into the top ten most ill-fated things a fictional character has said. But The Decagon House Murders, is neither a true pastiche or parody of Golden Age crime fiction. It purports itself to be the genuine thing, as part of the Honkaku (Orthodox) mystery tradition, in Japan, which according to the introduction is heavily indebted to authors such as S. S. Van Dine and Ellery Queen. This tradition as voiced by one of the characters in the book strongly believes that:

‘Mystery fiction is, at its core, a kind of intellectual game. An exciting game of reasoning in the form of a novel. A game between the reader and the great detective, or the reader and the author. Nothing more or less than that… What mystery novels need are… a great detective, a mansion, its shady residents, bloody murders, impossible crimes, and never-before-seen tricks played by the murderer.’

Judging the novel by its own criteria, I would say it does pretty well on the mansion with a mysterious past front and it certainly has its fair quota of gruesome deaths and impossible crimes. I’m not sure whether it includes ‘never-before-seen tricks’ but the ones it has are played extremely well and had me completely foxed, which is more annoying considering how fair it plays to the reader. The only thing I can say in my defence is that I kind of did and didn’t know who did it at the same time, which is perhaps what made it a bit more galling. The introduction was very helpful in contextualising the novel and the only thing which I disagreed with was the notion that the Golden Age tradition had ‘shut up shop’ in the UK. It may not continue in its purest form but I think it still has a presence. Moreover, I did start this novel with a small sense of foreboding when I read this part of the introduction:

‘His characters act almost like robots, their thoughts depicted only minimally through repetitive phrases. The narration shows no interest in sophisticated writing or sense of art and is focused solely on telling the story. To readers who were used to American and British detective fiction, The Decagon House Murders was a shock. It was as if they were looking at the raw building plan of a novel.’

Perhaps not the most encouraging way to set up a book. Looking back on the novel it is true the writing is not beautiful and the story is the entire focus, but I think it is only problematic and grating in passages where there is little dialogue. In a way you kind of forget about this aspect of the text as you progress through the novel as your mind becomes intent on unravelling the puzzle set before you, considering also it is responding to the theme set out by Christie.

The Decagon House Murders

The novel opens with the killer, unnamed of course, mulling over his plans to lure members of the K – University Mystery Club to Tsunojima, an island where 6 months ago Nakamura Seiji, his wife and his two servants were brutally murdered, only to then pick them off one by one in true Christie style. What perhaps makes this part of the text interesting is the precarious balance of sanity and insanity, as the killer simultaneously knows what he is doing is wrong, yet cannot prevent himself from taking on this god-like role.

The members of the mystery club, which read, write and discuss mystery fiction, all have nicknames based on famous crime writers: Ellery, Carr, Leroux, Poe, Agatha, Orczy and Van Dine. The club members decide to stay there for the week during their holidays, to rest, to write and to explore the ruins of the Blue Mansion and the Decagon House, which they are going to reside in; the previous murder case adding a thrill to the occasion. Like their Christie counterparts, they are also going to be cut off from help, as the fisherman who drops them off agrees to not look in on them. There are pre-existing tensions within the group, which are brought to the forefront before the killings begin.

One of the ways this story does diverge from the Christie original is that the story alternates between the group on the island and characters on the mainland. Kawminami Taka’aki, an ex-member of the mystery club receives an anonymous letter stating they are all responsible for the death of Nakamura Chiori, a girl who had died of acute alcohol poisoning at the previous New Year’s Eve party. The note has seemingly been sent by Nakamura Seiji and has also been sent to other members of the club and also Seiji’s younger brother. Of course alarmed at receiving such a note, Kawminami begins some investigations into the matter, drawing in a member of mystery club not on the trip, Morisu Kyoichi and a friend of Seiji’s younger brother to help him.

However, whilst these three are playing amateur sleuth, things have taken a darker and dangerous turn on the island with the appearance of 7 name plates delineating roles such as first victim, last victim, detective and murderer and the first body shortly follows with the first name plate glued to their bedroom door. From there on in the action on the island revolves around the remaining members (which rapidly dwindle over a matter of days) exploring the island for a possible outside killer to turning on each other, their knowledge of crime fiction influencing the nature of their discussions. Thoughts occasionally turn back to the original unsolved murder case with the question of whether Nakamura Seiji is still alive cropping up regularly and the evidence swings for and against the idea right until the end. Fewer thoughts turn to the death of Chiori and the minds of those who do are quickly extinguished by the killer. As the investigation stagnates on the mainland (no one thinking to pop across to the island to see if everyone is okay) and the group on the island becoming smaller and smaller, with characters committing the unforgiveable mystery fiction faux pas of walking outside alone at night, the narrative can only head towards an explosive and combustible end…

For those who enjoy locked room and impossible crimes, this novel has plenty of them as the story looks at both the murders which took place originally on the island as well as those happening now and there are even two secret rooms. Moreover, when the solution is revealed, if you didn’t get it like me, then you will want to kick yourself because as soon as it said you can instantly see the clues in the text retrospectively. Furthermore, some of the tricks used to pull it off are – dare I say it – of Christie quality and the novel does play around with a few of Father Knox’s rules in his Decalogue. Ayatsuji’s variation on Christies’s solution is very well done. However, I didn’t like so much the more open ended nature of the conclusion and would have preferred a more conclusive finish, but I guess that is down to personal taste.

Overall I think I have found it hard to decide how I feel about this book. The puzzle it sets and solves is of a high standard and the parts of the story dedicated to the island characters and their increasing fears and paranoia are really engaging. But on the other hand there parts of the text which are less enjoyable due to the sparse styling forewarned in the introduction and I think the mainland parts of the story although essential in many respects to the final solution, could have done with less sparse writing, as there was insufficient psychological drama to compensate for it.

Rating: If it has been based on the puzzle alone I would have given 4/5 but due to other considerations such as writing style I went for 3.5 instead, as I think 3/5 wouldn’t have done justice to the puzzle. (And yes, 16 hours after reading this I may be over thinking this, still)


    • It’s okay, you’re not compelled to read every book I post about! (Only the really good ones). There are a lot of Golden Age detective authors and you could easily take a lifetime or two to get through them. That’s what it feels like to me anyways. I am a Golden Age fan but I like to mix it up with more modern texts, especially translated crime fiction, as its almost like a book palette cleanser and provides a change of pace and scene, as reading for example many country house murders in a row can get a bit samey. Mixing the books up, for me anyways, helps to keep it fresh.


  1. I really enjoyed The Decagon House Murders when I read it, though I’ll admit a bias for pretty much anything Locked Room International undertakes. The Paul Halter books , and particularly the two Derek Smith novels, they’ve published are absolutely worth checking out.

    I know what you mean about the writing style of TDHM being a little jarring (the dialogue attribution for one thing), but I’m willing to put that down to cultural ignorance on my part as I’ve read no other Japanese detective fiction. The Tokyo Zodiac Murders by Soji Shimada (author of the introduction the TDHM) has just been reissued, however, and is supposed to be the classic that motivated that honkaku school in Japan, so I’m looking forward to reading that sometime soon.

    Liked by 1 person

    • I haven’t heard of those two authors before so I shall have to check them out, as my reading of locked room mysteries could do with extending, having mostly been centred on authors like Carr. This is the first crime fiction novel I have read translated from Japanese but I have read a collection of Japanese crime short stories edited by John L. Apostolou, which were quite good as far as I can remember, one of which I think was mentioned in TDHMs introduction: The Psychological Test” by Edogawa Rampo.


  2. I enjoyed your review very much. I recently read this, thanks to a positive write-up from a fellow Golden Age fan on Facebook. I don’t think the characters were as wooden as described in the intro, but there was definitely something missing….some plot or character development during the killing spree. I can’t help comparing this (perhaps unfairly) to Christie’s classic, but although the characters in And Then There Were None did not know each other before the island, I feel they are much better realized characters than the circle of friends in Decagon House. If you’re going to have people know each other within the circle of suspects, I’d like to see better development of those relationships than we find here.

    I liked the twisty solution, though, and I didn’t mind so much the open ending; I think that’s a very Japanese thing! I wish more of these Honkaku mysteries were translated into English. I wouldn’t mind reading a few more!

    Liked by 1 person

    • Glad you enjoyed my review and I definitely agree about there being something missing from the characters in The Decagon House Murders. I did read a collection of Japanese crime fiction short stories, which was quite good. It’s called Murder in Japan: Japanese Stories of Crime and Detection and its edited by John L. Apostolou. So what sort of crime fiction do you usually read?


  3. I’ve just – and only just – finished reading the English translation released by LRI, which would be my second time reading ‘Decagon House Murders’. I read it in Chinese the first time round, and it left me feeling that the twists were very clever – but were hinted at rather than specifically clued.

    Having read it in English (my first language), I think I would affirm my initial impression? There doesn’t seem to be any clues in the narrative that would allow a detective to prove the guilt of the culprit. Or did I miss something…?

    Liked by 1 person

    • My memories aren’t the sharpest on this, but I think you might well be right, as what I can remember of the solution made me think of the narrative clues for the reader, yet which aren’t available to the detective character in the book. I think it is the dryness of the prose style is what I remember most.


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