‘I see.’
‘The only problem,’ Utsumi continued, ‘is that they can’t figure out how the killer did it. So how was it done? We’ve got the results from Spring-8 you wanted. Surely you can reveal the trick now.’
Yukawa rolled up the sleeves of his white lab coat and crossed his arms. ‘Forensics couldn’t figure it out?’
‘They say there’s only one possible method: you would have to remove the hose from the filtration system, put the poison in, then reattach it. But that would leave certain telltale signs – marks on the hose or whatever – which they didn’t find.’
‘And you have to know exactly how it was done?’
‘Of course. If we can’t prove how the crime was committed, it doesn’t matter if we have a suspect.’
‘Even though you found the poison?’
‘We won’t have a chance in court if we don’t know how the crime was committed. The defence will claim police error.’
‘Oh?’
‘They’ll say that there’s a possibility that some of the arsenous acid in the coffee made its way to the filtration system after the fact. We are talking about trace molecules here.’
Yukawa sat back in his chair, nodding his head slowly. ‘They might make that argument, it’s true. And if the prosecution couldn’t provide a means of insertion, the court would have to listen to the defence.’
‘Which is why we really need you to explain how it was done. Please. Forensics wants to know, too. Some of them even wanted to come with me to hear it from you firsthand.’
‘Well, that won’t do. I can’t have police tromping through my lab.’
‘Which is why I came by myself. Well, and Detective Kusanagi’s coming later on.’
‘Speaking of which, shouldn’t we wait for him to get here? I don’t want to have to repeat my explanation. Also, there’s one last thing I need to check first.’ Yukawa lifted an index finger. ‘In your department’s opinion – no, actually, your personal opinion is fine – what was the motive for the murder of Yoshitaka Mashiba?’
‘Well, I think romantic troubles would pretty much sum it up.’
Yukawa frowned. ‘Isn’t that a rather abstract motive on which to rest your case? Try telling me who loved whom, who hated the victim enough to kill him, and why.’
‘Well, it’s all conjecture at this point …’
‘Fine. Like I said, all I’m looking for is your personal opinion.’
Utsumi nodded; she lowered her eyes, collecting her thoughts.
Steam bubbled from the coffeemaker. Yukawa stood and retrieved two coffee mugs from the sink.
‘Well,’ Utsumi said as he began to pour the coffee, ‘I think Ayane Mashiba did it. Her motive was that she felt her husband had betrayed her – not just because he asked her for a divorce when he decided she couldn’t bear him children, but also because he had started seeing another woman. That’s what pushed her to murder.’
‘Do you think she made up her mind the night of the party at the Mashiba house?’ Yukawa asked.
‘She probably made her final decision that night, yes. But I think it’s likely she had started harbouring murderous intentions a little earlier than that. She knew about Yoshitaka and Hiromi Wakayama. She also had intimations of Hiromi’s pregnancy. Yoshitaka’s declaration was the final straw.’
Yukawa returned to the table, holding a coffee cup in each hand. He placed one in front of Utsumi. ‘What about this woman, Junko Tsukui? Did she have nothing to do with the murder, then? Isn’t Kusanagi out there right now questioning people about that?’
The likelihood of a personal connection between Junko Tsukui and Ayane Mashiba was the first thing Utsumi had mentioned to Yukawa when she got to the lab.
‘I wouldn’t say there’s no connection. It’s likely that the arsenous acid used in this murder was the same that Ms Tsukui used to kill herself. If Ayane was close to her, she would’ve had an opportunity to get the poison from her.’
Yukawa raised his cup and his eyebrow at Utsumi. ‘And then?’
‘Excuse me?’
‘Is that all Junko Tsukui had to do with it? She just provided the poison? Her death doesn’t factor into the motive at all?’
‘Well, it’s hard to say …’
Yukawa smiled thinly and sipped his coffee. ‘Then it’s hard for me to tell you the trick.’
‘What?! Why?’
‘Because telling you would be far too dangerous. You haven’t yet figured out what this case is really about.’
‘And you have?’
‘More precisely than you.’
Utsumi was glaring at Yukawa, both hands clenched around her mug, when they heard a knock at the door.
‘Good timing! Maybe Kusanagi can shed a little light on the subject,’ the professor said, rising to his feet.
TWENTY-EIGHT
As soon as Kusanagi walked into the room, Yukawa asked how the latest questioning had gone. After a moment’s hesitation, the senior detective told them what he’d heard from Ikai.
‘Yoshitaka Mashiba talked to her first. Which pretty much dismantles your theory, Utsumi,’ Kusanagi said, with a sidelong glance at the junior detective. ‘I mean, the idea that Ayane used the party as a way to get close to him.’
‘It was less a theory than it was a possibility.’
‘Okay. Well then, it’s no longer a possibility. So what do you think happened now?’ He turned to look at her directly.
Yukawa offered Kusanagi a mug of coffee. The detective nodded in thanks.
‘What do you think?’ Yukawa asked his friend. ‘If we accept what Mr Ikai told you at face value, then the couple first met at that party. Which would make the fact that Mr Mashiba’s ex was Ayane’s friend a simple coincidence. How does that sit with you?’
Kusanagi sipped his coffee, sorting out his thoughts. He opened his mouth to speak, then hesitated, tapping his fingers on the tabletop.
Yukawa grinned. ‘So you don’t believe the lawyer?’
‘Ikai’s not lying,’ Kusanagi said at last. ‘But there’s no proof that what he saw was the truth.’
‘Go on.’
Kusanagi took a breath before saying, ‘It could have been an act.’
‘A performance?’
‘Yes. Intended to give the impression that it was their first meeting … in order to hide the fact that they had a relationship before the party. Ikai was brought along so that there would be a witness. A mobile phone case on a bar leading to true love is a little too perfect.’
‘Perfect indeed,’ Yukawa said, a spark in his eye. ‘And I happen to agree with you. Let’s see what the lady thinks.’ He turned to Utsumi.
She nodded. ‘It makes sense. But why go through all that trouble?’
‘That’s the rub, isn’t it? Why put on an act?’ Yukawa looked at Kusanagi. ‘What do you think they were up to?’
‘It’s simple. They were trying to hide the truth.’
‘And what truth is that?’
‘The truth of how they actually met. Which would have been through Junko Tsukui. A fact which they didn’t want getting out, what with her being Mashiba’s former girlfriend, and dead besides. They needed to create a situation where they could meet again, for the first time, under different circumstances: the party.’
Yukawa snapped his fingers. ‘An excellent theory. Unas -sail able, really. So let’s talk about how they really met. More to the point, when they fell in love. Was it before or after Tsukui committed suicide?’
Utsumi took a deep breath, straightening in her chair before she looked towards Yukawa. ‘Do you think Ms Tsukui committed suicide after Mr Mashiba started seeing Ayane?’
‘It makes sense. Imagine her, betrayed by both her lover and her friend. That would be quite a shock.’
Kusanagi felt his heart sinking into darker depths. What Yukawa was suggesting did indeed make sense. That scenario had occurred to him as well while he was in the middle of his chat with Ikai.
‘That certainly clears
up the point of that party,’ Utsumi said. ‘With Mr Ikai there to testify that the two had met for the first time while he was watching, they would be able to deny any connection between their relationship and Junko Tsukui’s suicide.’
‘See? Now we’re getting somewhere,’ Yukawa said, a satisfied look on his face.
‘Should we confront Mrs Mashiba about it?’ Utsumi wondered out loud, looking towards Kusanagi.
‘Confront her how?’
‘What if we showed her the picture book, the one with the tapestry in it? Doesn’t that prove they knew each other?’
Kusanagi shook his head. ‘All she’d have to say is, “Sorry, no idea”.’
‘But …’
‘She’s been hiding her friendship with Yoshitaka’s ex – even the fact that she knew he had an ex at all. If all we do is bring her some picture books, we won’t get anywhere. We’d simply be tipping our hand.’
‘I have to agree with Kusanagi,’ Yukawa said, stepping over to the chessboard and picking up a black pawn. ‘If you’re going for checkmate, better do it in one move, or you’ll have a stalemate on your hands.’
Kusanagi looked at the physicist. ‘So – she did it.’
Yukawa remained at the chessboard. ‘This next part is the most important. Now that we know a little more about Mrs Mashiba’s past, how does that knowledge relate to the case at hand? Is the arsenous acid really the only connection?’
‘Maybe,’ Utsumi said thoughtfully, ‘Mrs Mashiba couldn’t forgive her husband for leaving her especially because of what their relationship had done to her friend?’
‘I could see that,’ Yukawa said, nodding.
‘No,’ Kusanagi said, ‘that’s not how she would think about it. She betrayed her friend and stole her man – just as her assistant betrayed her and stole her husband.’
‘Karma, then? So she would just resign herself to her fate?’ Yukawa said. ‘No hatred towards her husband or his lover – is that what you’re trying to say?’
‘Not exactly …’
‘I think there’s a question both of you need to ask.’ The physicist turned away from the chess set, catching both detectives with his stare. ‘Why do you think Yoshitaka Mashiba switched from Junko Tsukui to Ayane?’
‘I don’t know,’ Utsumi said, ‘probably just a change of heart—’ She put her hand to her mouth. ‘Oh. No, that’s not it, is it?’
‘It’s not,’ Kusanagi said. ‘He left her because she didn’t give him a child. Remember, Mashiba was ready to marry any woman who’d get pregnant for him. If it looked like she couldn’t, he would switch.’
‘That fits with everything we’ve heard thus far,’ Yukawa agreed. ‘So the question is, did Ayane know his reason at the time? Did she think Yoshitaka left Junko and chose her because he thought she would bear him children?’
‘Well …’ Kusanagi fell silent.
‘I doubt it,’ Utsumi said crisply. ‘What woman would want to be chosen like that? If she realized it at all, it was just before they got married – when they arranged to split up if she couldn’t get pregnant within a year.’
‘That’s what I think, too,’ Yukawa said. ‘So let’s talk about motive again. You mentioned that Mr Mashiba’s betrayal was the motive, Utsumi, but was what he did really a betrayal? After one year, there was no pregnancy, so he asked for divorce and hooked up with another woman – wasn’t he just living up to the agreement they made?’
‘That’s true; but emotionally speaking, how could she accept that?’
Yukawa smiled. ‘So let’s phrase it a different way: if we assume that Ayane was the killer, then her motive was that she didn’t want to honour her own promise. Correct?’
‘I guess you could say that.’
‘What are you driving at?’ Kusanagi asked his friend.
‘Try to imagine how Ayane was feeling just before she got married. What were her intentions when she made that agreement with Yoshitaka? Was she optimistic that she could get pregnant within the year? Or had she decided that, even if she didn’t get pregnant, her husband wouldn’t follow through on his end of the deal?’
‘Both, I’d say,’ Utsumi answered.
‘Okay. Let me ask you this, then: if she thought there was a chance she might get pregnant, wouldn’t she have gone to the hospital?’
‘Hospital?’ Utsumi furrowed her brow.
‘According to what you’ve told me, not once during the year did Ayane undergo infertility treatment. With a promise like the one this couple had made, I would have expected her to start visiting a gynaecologist within a few months of the wedding.’
‘According to what Mrs Mashiba told Hiromi Wakayama, they hadn’t tried infertility treatments because those take too long.’
‘That would be Mr Mashiba’s thinking. Why bother with all that time and money when it would be quicker to simply find a new wife? But what about Ayane’s perspective? Wouldn’t she want to try anything, even if it meant grasping at straws?’
‘Yeah, sure,’ Kusanagi muttered.
‘So why didn’t she go to the hospital? Therein lies the key to this case.’ Yukawa adjusted his glasses with one finger. ‘Think about it. She had time, she had money. So why wouldn’t she go?’
Kusanagi thought. He tried to put himself in Ayane’s shoes, but no answer was forthcoming.
Suddenly, Utsumi stood. ‘Maybe she didn’t go because she knew there was no point.’
‘No point? What do you mean?’ Kusanagi asked.
‘What if she knew any treatments would be pointless?’
‘Exactly,’ Yukawa said. ‘She knew going to the hospital would do nothing for her. That’s why she didn’t go. It’s the most logical explanation.’
‘So … she knew she was completely infertile,’ Utsumi said.
‘She was over thirty. Surely she’d had at least one gynaecological exam by that age. Maybe she had been told earlier that she couldn’t have children. If so, not only would there be no point in going to the hospital, there would also be the danger that if she did go, her husband might learn the results.’
‘Wait a second. You’re saying that she made that bargain with her future husband even though she knew she couldn’t have children?’ Kusanagi asked.
‘That’s what I’m saying. Her only hope was that her husband wouldn’t follow through on his threat. Of course, he did, with flying colours. So, she decided to kill him. Now, let me ask you – when did she first contemplate killing Yoshitaka Mashiba?’
‘When she found out about him and Hiromi—’
‘No, that’s not it.’ Utsumi cut Kusanagi off. ‘If she had planned on killing her husband if he kept the promise, then she made up her mind when she made the promise.’
‘That’s the answer I was waiting for,’ Yukawa said, his face taking on a sudden sober intensity. ‘Essentially, Ayane predicted that, within a year’s time, she would have reason to kill her husband. Which meant it was possible for her to prepare the means to kill him in advance.’
‘Excuse me? Prepare?’ Kusanagi’s eyes widened.
Yukawa looked over at Utsumi. ‘You told me what For -ensics thought when they examined the filtration system – that there was only one way to get the poison in there, which was to remove the hose, insert the poison, then reconnect it. Correct? Well, Forensics was absolutely right. That’s exactly what happened … one year ago.’
‘No way,’ Kusanagi spluttered, then fell silent.
Utsumi shook her head. ‘But – if she did that, she couldn’t have used the water filter!’
‘That’s right. She didn’t use the water filter for an entire year.’
‘But that just doesn’t make sense. Wasn’t there evidence that the water filter had been used?’
‘The crud in the filter wasn’t from the past year. It was from the year before.’ Yukawa opened his desk drawer and produced a piece of paper. ‘Remember when I had you check on the filter part number? Well, I called up the maker and asked when that particular part was on the market
. It turns out that number range was used two years ago. They went so far as to say it was highly unlikely a part with that number had been used to change a filter only one year ago. In other words, when they changed the water filter a year ago, our killer immediately replaced the new filter with the old one, thinking that if the filter was found to be unused after the poisoning, she’d be discovered. That’s when she put in the poison.’
‘Impossible,’ Kusanagi whispered, his voice hoarse. ‘That’s simply impossible. You’re saying she put the poison in, then didn’t use the filter for a whole year, not even once? It doesn’t make sense. What if someone else had used the water from the filter? How dangerous is that?’
‘Very,’ Yukawa agreed coolly. ‘But she pulled it off. For an entire year, whenever her husband was home, she never went outside, and she never let anyone else near the kitchen water system. Whenever they held a party at their house, she did all the cooking. And she always had bottled water in good supply, making sure they never ran out. Everything to ensure that her plan worked.’
Kusanagi shook his head several times. ‘I don’t believe it. It’s impossible, Yukawa. Show me one person capable of pulling that off.’
‘Actually, it is possible,’ Utsumi said. ‘Yukawa had me ask all kinds of questions about the couple’s life after they got married. I talked at length with Hiromi Wakayama. Even though I didn’t know why I was asking the questions at the time, I get it now. You were checking whether anyone other than Mrs Mashiba had a chance to touch that water filtration system, weren’t you?’
‘Correct. The most compelling piece of evidence by far was how the Mashibas spent their days off. Ayane would sit on the living room sofa, working on a patchwork all day long. Why did she choose that room? So she could keep an eye on the kitchen.’
‘You’re delusional,’ Kusanagi said, his voice almost a groan.
‘Logically speaking, it’s the only possible answer. Our killer was extraordinarily tenacious, and extraordinarily strong-willed, you have to admit.’