Free The Decagon House Murders by Yukito Ayatsuji

time of death for both of them was the afternoon of September 19th—the day before the fire.
    Nakamura Kazue had been strangled to death, on the bed in her bedroom, with a rope-like object. The left hand of the body was missing from the wrist down, and had been cut off after death. The whereabouts of the hand are still unknown. Her estimated time of death is sometime between September 17th and 18th.
    Nakamura Seiji had been completely doused in kerosene and burnt to death in the same room as Kazue. Large quantities of sleeping medicine had been found inside his body, and this was the same for the other three victims. Estimated time of death was the early morning of September 20th, when the fire broke out.
    The fire is thought to have started in the kitchen. The murderer had splashed kerosene all over the mansion and then set fire to it in the kitchen.
    ‘As you know, the police have set their minds on the theory that the missing gardener is the murderer. But there are still points that remain unclear.
    ‘For example, the problem of Kazue’s left hand. What reason could Yoshikawa have had for cutting off the lady’s hand and taking it with him? And there’s the problem of his escape route. The only motorboat on the island was still in the inlet. He could have hardly killed four people and then gone swimming across the sea to the mainland in late September. The police, of course, also looked into the possibility of the murderer being someone from the outside, but that theory seemed to fit less and less the further they pursued it. The rough outline of the case as proposed by the police based on the “Yoshikawa equals murderer” theory is—Don’t mind me, please eat your meal.’
    ‘Wha—oh, yes.’
    Kawaminami’s pizza toast and coffee had been brought during Shimada’s explanation. It was not because he was being polite that he had not touched it. He had been so intrigued by Shimada’s story he had forgotten to eat.
    ‘Motives. They came up with two. The first was that he wanted Seiji’s fortune, so: robbery. The other is that he had feelings for Kazue, or that they had secretly had a relationship. It was probably a combination of the two.
    ‘Yoshikawa first knocked everybody out with sleeping medicine before he started his crime spree. He tied Kazue up, did the same to Seiji and locked him up somewhere else. He then took Kazue to the bedroom and satisfied himself with her. Kazue was the first to be killed, and her estimated time of death was one or two days earlier than that of the other three victims. While there is no definite proof, it appears that he raped Kazue after her death. The Kitamura couple were murdered next. They were probably still asleep because of the sleeping medicine. And Seiji was last. Yoshikawa doused Seiji with kerosene in his sleep and then went to the kitchen to start the fire.’
    ‘But, Mr. Shimada,’ Kawaminami asked, pausing with his cold coffee in mid-air, ‘why did the murderer keep Seiji alive until then? The same for the Kitamura couple. If he was going to kill them anyway, wouldn’t it have been safer to do it right away?’
    ‘He might not have planned to kill them right from the start. He might have panicked after he killed Kazue. The fact he saved Seiji for last does support the idea that the motive was robbery.’
    ‘Why?’
    ‘Because of Nakamura Seiji’s characteristics as an architect .’
    ‘Nakamura Seiji as an architect?’
    ‘Yes. I told you just now that Seiji was a bit peculiar. There is a certain monomania, a childish touch, a playful heart to be sensed from all the buildings Nakamura Seiji designed, including the Blue Mansion and its annex building the Decagon House. They are all a showcase for his peculiar tastes. One of them being what you might call a love of gimmicks .’
    ‘Gimmicks?’
    ‘Yes. I can only take a guess at the number, but the burnt-down Blue Mansion was full of gimmicks like hidden rooms, cabinets and vaults. Only Nakamura Seiji