Like last week's regular review, this novel too is set around New Year. Weird coincidence that I happened to read these two novels one after another, and if I hadn't bumped up another review to be my first of the year, these two reviews would have been posted in the first week of the new year.
The last time I bothered to check, Nishimura Kyoutarou had over 600 novels on his resume. Most of them are of course about train-related mysteries featuring Inspector Totsugawa: there's a reason why people in Japan instantly associate the train mystery and elaborate alibi tricks using ingenious use of railway schedules with Nishimura (see for example this Sandwichman sketch, where Nishimura's name is used as a punchline for a gag about railway schedules). But as you can guess, churning out three, four novels a month will have effect on the quality of the mystery plots, and the couple of Nishimura novels I read once he started to be this extremely prolific were not particularly enjoyable or inspiring. I did have fun with several of his earlier novels though, including the weird crossover series with Ellery Queen, Hercule Poirot, Akechi Kogorou and Inspector Maigret, and once in a while, I enjoy exploring his earlier output.
Koroshi no Soukyokusen ("Hyperbola of Murder", 1971) is one of Nishimura's earlier novels and widely considered to be one of his best works, and it isn't even about Inspector Totsugawa or railway schedules! In fact, it's a very diferent type of story than we are used to with Nishimura, as it's a closed circle murder mystery that is written as a full-blown homage to Agatha Christie's And Then There Were None. Though with a very interesting twist. For once you open the novel, you'll find a short preface by the author, where he tells you outright that the main trick of this novel revolves around twins! Figuring that Knox and S.S. Van Dine had certain strong opinions about the use of twins in mystery fiction, Nishimura simply decided to make it clear right away that Koroshi no Soukyokusen will make use of twins as a plot device, as you can hardly complain that the reader has not "been duly prepared for them" with such a warning! And indeed, the story starts off right away showing how a pair of twin brothers have been committing a series of curious robberies on small supermarkets and other stores in Tokyo at the end of the year. Each of these stores was robbed by a man with a pistol, but for some reason, the robber did not wear a mask. Eventually, the police manages to find this man, and twice even! For apparently, the robber has a twin brother, but both of them deny having committed the robberies despite not being able to present any alibi, and with no other evidence but the visual identification by the victims, the police can't do anything: they know the brothers must be in cahoots, but as the robberies were ultimately only committed by one person, they can't arrest both brothers, as one of them is not guilty of any crime in the practical sense. The police also has trouble locating where the stolen money has gone too.
At the same time, the reader is introduced to Kyouko, a typist who works in Tokyo, but is now spending New Year at a small hotel in the Miyagi Prefecture. She and her fiancé are among the lucky six inhabitants of Tokyo who have been offered a ski holiday completely free of charge at the Snow-View Hotel as a form of promotion: the owner, who runs the whole hotel by himself, hopes these guests will help promote the hotel to friends and acquaintances in Tokyo after their stay. Among the other guests are a student of criminology, a taxi driver and a girl working in a not-so-legal massage parlor. The Snow-View Hotel is located deep in the snowy mountains and at this time of the year basically only accessible by snowcat or skis. It doesn't take long for one of the guests to be find hanging from the ceiling in his locked room though, accompanied by a card with a strange circle mark and the message "Thus The First Step Of My Revenge Is Completed." Coincidentally, they realize that one of the bowling pins in the entertainment room has been removed too. They try to phone for help, but the phone line has been cut and even the snowcat has been disabled, meaning they are all trapped in the hotel for now. More murders soon follow, and the remaining guests sart to suspect each other. Eventually, the survivors manage to call once for help, but by the time the police arrives at the hotel, it's already too late: they find seven bodies in and around the hotel. At first, the police suspects one of the victims here must have killed the others and then themselves, but then the police receive an anonymous letter connecting these murders with the robberies committed by the twins, but what could that connection be?
Well, you certainly can't accuse Nishimura of not being ambitious here. First you have the daring declaration of the usage of twins at the very start of the novel, and then we are introduced to a dual narrative structure, with the second storyline obviously being inspired by And Then There Were None. In fact, even the characters locked up in the hotel themselves realize their situation is very much like And Then There Were None (including the bowling pins that disappear each time someone is killed), though unlike And Then There Were None, the characters here don't really know why they are being killed: they have not been accused of crimes like And Then There Were None, and none of them know each other. They have nothing in common, so why were they chosen to be killed? Don't try too much thinking about this yourself though: there might be a minor clue pointing at what connects these people, but the exact reason for why these people are killed is not something you can properly deduce based on what is shown in the story, and you just have to wait for the reveal. It's kinda farfetched though, to see the killer go this far because of that reason. I've seen the same idea used in other mystery stories too, but I find this particular iteration the least convincing.
Anyway, perhaps the most interesting part of this novel is how it's a homage to And Then There Were None, using a dual narrative structure. I won't be the only one to be reminded of works like The Decagon House Murders (disclosure: I translated the English version) or The Jellyfish Never Freezes, which tackle the same story format. The dual story structure is a bit crude here though compared to these examples. In both The Decagon House Murders and The Jellyfish Never Freezes, the connection to the two narratives is very clear to the reader: in the former, we follow a series of murders on an island, while we also follow an investigation into the background of those murders on the mainland, while in the latter, we see the murders occur in real time, but also follow a narrative that is set a few days after the murders. In Koroshi no Soukyokusen, this connection is not clear at all until the very end. Each chapter, you have a section about the robberies committed by the twins and a section set at the Snow-View Hotel, but you never understand why you are reading about these completely different storylines. It results in a disjointed reading experience, as the story keeps jumping between these completely different events. Obviously, the connection between them is explained in the conclusion, and there is both an in-universe and a more meta-explanation to it, but both reasons feel a bit weak: the in-universe reason is incredibly convoluted, with far too many steps to get the intended results. The meta-reason is... your mileage may vary. I understand why, but it doesn't really work very well, even I find it interesting Nishimura declared outright he'd be using twins for this novel.
The robber-twins narrative is entertaining though, focusing on the police inspectors who know the twins are working together to ensure the actual robber of the two isn't caught, but they can't figure out where the loot went or how to pin the evidence on the actual robber. Meanwhile, the Snow-View Hotel narrative is definitely a straight-up homage to And Then There Were None. And as you can guess: the mystery for the reader at the end revolves around how the killer managed to kill seven people in a hotel surrounded by snow, and escape without the police finding any trace of them. I personally find these And Then There Were None homages the most fun when they have a solution to how it was all done that can be explained simply with one sentence, that makes you think "Aha, so that what it was!' the moment you hear it. That's definitely the case here, but while I think the basic idea is okay, it's just never going to work in a practical sense. I am the last person to be looking for realism in my mystery fiction, but the culprit's scheme here depends a lot on factors they can not exactly control, and 9 out 10 times, this would've blown in their face immediately, and there's no retries here. In a story with a smaller scale, this idea might've worked better, but even when I figured out what happened, I still couldn't believe it any culprit would go through all this trouble only to have the most crucial part of the scheme depend on pure luck, and the odds here weren't even in their favor from the start: they'd be betting on things happening in a manner that usually wouldn't occur like that and it would be difficult to influence the events in a way to become more favorable. I think the seasoned genre reader won't have too much identifying who the culprit is and how it was done,
Koroshi no Soukyokusen is definitely one of the best-plotted Nishimura Kyoutarou novels I've read, and as an And Then There Were None homage, it's quite entertaining, but some parts of the plot do feel weak/not very convincing. It has interesting ideas like the twins declaration and the core And Then There Were None variation that make it stand out, but perhaps the plot is telegraphed a bit too obviously, especially near the end when the story moves into the final act. But still an amusing read if you want read a Nishimura Kyoutarou novel that is not like the Stereotypical Nishimira Kyoutarou Novel.
Original Japanese title(s): 西村京太郎『殺しの双曲線』