The Decagon House Murders by Yukito Ayatsuji is a locked room murder mystery in the tradition of Agatha Christie’s And Then There Were None. Originally published in the 1980’s, it is about a group of university students who are in a mystery club and who go to stay on an island for a week. The appeal of the island is that four people were murdered there previously and the main residence burned to the ground. Rumors circulate that the ghost of the original owner haunts the island.
Strangely enough, I found the parts of the story that happened off-island more interesting than the one-by-one murders happening on the island. Ayatsuji’s writing in this is purposefully simple, making each character fit their role and nothing more. There is also no speculation on the heart of man, the state of the world, and larger themes that Christie in particular often speculates on in her stories, and there’s little to no romance. Decagon is about the mystery alone. In the off-island scenes, Ayatsuji introduces an amateur detective only incidentally related to the other characters, and he was the main intrigue for me in the story. I thought if I followed his thinking I would solve the mystery. Even so, I didn’t guess who the murder was.
With this book, Ayatsuji reinvigorated the Japanese mystery tradition called honkaku, a tradition in which the focus of the story is the mystery only and in which the characters have a blankness much like characters in a video game. Fellow mystery writer Soji Shimada writes a great introduction explaining this, and it’s well worth the read. The honkaku style is supposed to be a true game for the reader, using fair play rules and clues so that he has a chance at guessing the culprit before the story ends. Again, I wasn’t able to guess, but at some point I do plan to read it again to determine what I missed that I should have picked up on.
It is also possible translation could be an issue here. At times it didn’t seem like the English really matched the story well, and Ayatsuji’s word play is probably a lot more fun in Japanese. Many times I wasn’t sure who was speaking, and also wasn’t sure if that was purposefully confusing. That all being said, once we get the full explanation for the murders, I’m not so sure literary trickery and devices weren’t used. It didn’t seem like something a reader could glean from the information given, but I maybe just didn’t pay enough attention. There were likely a lot of clues that I just didn’t pick up on.
The best part of The Decagon House Murders is the house on the island and the fact that all of the characters go by their mystery club names, not their actual names. The mystery club names are taken after English mystery writers: Christie, Poe, Ellery, etc. There are also a lot of good discussions not unlike those in the movie Scream in which the characters talk about the tropes and devices in horror stories, only here it’s with mysteries, specifically locked room mysteries. As in And Then There Were None the “locked room,” in this isn’t a room, but the whole island, and the Decagon house in itself is a snare both to the characters and to the reader as we are constantly focusing on it as the locked room.
I plan to read more honkaku mysteries in the future and find this idea of a more literal puzzle story for readers to figure out, a good one. My family and I are really into playing Escape Room these days, and those are also locked room mysteries. I missed having a Poirot or Sherlock or main quirky detective to follow, though.