It felt odd, returning to Marble Hall in the back of a police car with Wardlaw driving and Blakeney next to her, but they still hadn’t released my MG – it was now being used as evidence against Elaine Clover – and I didn’t fancy the train. We turned into the gates and drove through woodland. For the first time, I noticed the ruined cottage where three children had once hidden themselves away, pretending to be a secret society called the Rogue Troopers to plot the murder of their grandmother. I leaned forward as the main house came into view, its ivy and gabled windows, its wings and towers all bolted together as if in homage to every Golden Age mystery. It all felt completely right. This wasn’t just the end of a journey but the laying to rest of any number of ghosts.

The car park was empty. DI Blakeney had insisted that the house should be closed to the public while we were there and although Jonathan Crace had grumbled – the loss of even a single day’s revenue was a blow to him – he had been forced to comply. The Little Parlour Tea Room was dark. The gift shop was selling no gifts. The entire house had an unwelcoming feel that no tourist would have noticed but which made it truly authentic for the first time since the death of Miriam Crace.

Frederick Turner was waiting for us at the main entrance and as he limped towards the car, more worn out than he had been the last time I came here, who else could I think about but Frédéric Voltaire? I had met Frederick most recently at the party and he had seemed more conciliatory, but I wondered how he would greet me now. I remembered how offended he had been by what he saw as my attack on Miriam Crace and how he had virtually thrown me out. I didn’t think he’d be happy that I’d returned.

I was in the company of two police officers, though, and that made a difference, and as for Frederick, he was there in an official capacity – to open the door and show us in. He was reserved but polite, addressing himself more to Blakeney than to me. ‘The others are waiting for you in the dining room. I’m afraid the kitchens are closed, but there is coffee in in the room. If there’s anything else you need, please let me know. This way …’

As he showed us through the silent house, the lights off and the rooms all empty, it occurred to me that this was how Frederick had lived for the last seven years, still trapped in the same building where he had been brought as a child. He’d once joked that he might come back to haunt the place, but in a way he already did. Everyone else had gone. Miriam was dead and now Eliot was too. What must it be like to endlessly walk these corridors and stairways as the only living memory of what had once been? Every day, when the tourists left and the ticket sellers and the other ladies went home, he would be here on his own, making his way up to the suite of rooms that he still occupied on the second floor. And what then? A box set on Netflix? A pile of books? A ready-prepared dinner-for-one heated up in a microwave? It would have driven me mad.

He showed us into the dining room, which I had already visited but which had made little impact on me when I first saw it. This time, I wondered if Eliot hadn’t used many of its features as inspiration for the petit salon where the Chalfonts had taken their breakfast. There were the same double windows, the antique rosewood dining table, even a grandfather clock. I noticed a painting on the wall: a vase of tulips, which, though clearly not painted by Cézanne, could have been the inspiration for the masterpiece that Eliot had described. There was an unpleasant smell in the air, a mustiness that I’d somehow missed the last time I came here. Perhaps it had been less apparent when the place was filled with tourists. It was the smell of loneliness, of a lifestyle long forgotten.

Three people were waiting for us.

Jonathan Crace was at the head of the table. Of course. Where else would he have chosen to sit? Today, he was wearing a blue blazer and striped tie. They went well with the ginger hair and the signet ring. Roland Crace was next to him, already avoiding my eye and looking nervous … as well he might. The last time we had spoken, I had accused him of cheating on his own brother and he had thrown me out of Eliot’s house. At the other end of the table, keeping her distance from her brother and her uncle, Julia Crace didn’t look at all happy about being dragged down here from Lincoln. I wondered how Blakeney had managed it. Had he threatened to arrest her if she failed to show up?

None of them was pleased to see me. For the moment, they said nothing. But I could tell that Jonathan Crace was furious. He must have been informed that I’d had nothing to do with Eliot’s death, but I’m sure he still saw me as the architect of all his misfortunes.

Frederick Turner hovered at the door. ‘I’ll leave you to it,’ he said.

‘I think you should stay with us, Mr Turner,’ Blakeney said. ‘You were here from the very start and I’d have said you were very much a witness to what happened.’

‘Are you sure?’ Frederick glanced at Jonathan as if asking his permission to remain.

‘If the police officer wants you to stay, you might as well sit down,’ Jonathan snapped. ‘By the way, the coffee is revolting. I don’t suppose you can make some more?’

There were two coffee flasks and a plate of biscuits on the table. I was reminded of my initial meeting at Causton Books. That could have taken place a century ago.

‘Yes. I can go to the kitchen—’

‘I think we can manage without coffee, if you don’t mind, Mr Crace,’ Blakeney said, not hiding his distaste. The way Jonathan had spoken, he could have been addressing a waiter or a servant. He closed the door as Frederick reluctantly took his place at the table, keeping as far away from everyone else as he could. Wardlaw and Blakeney sat next to each other. I took a place opposite Julia.

‘Why is she here?’ Roland asked, his voice utterly flat and unfriendly. He meant me.

‘I know it’s unorthodox,’ Blakeney replied. ‘But it was Ms Ryeland who asked for this meeting. Given that she was working with Eliot and was unfairly accused of his murder, I felt she had a right to a hearing.’

I expected Wardlaw to show her disapproval but Blakeney must have had a word with her because for once she kept her thoughts to herself.

‘Forgive me.’ Jonathan Crace didn’t sound remotely apologetic. ‘Are you telling me that you’ve made us come all this way simply to listen to this woman complain about the way she was treated?’

‘No, sir.’ Blakeney looked as angry as I felt. ‘There’s rather more to it than that.’

‘Does she know who killed Eliot?’

‘Yes. As a matter of fact, I do,’ I said. I couldn’t hold back any longer. I looked him straight in the eye.

‘So why don’t you tell us?’

‘Eliot was killed by the same person who murdered Miriam Crace.’

Jonathan swallowed, as if he had accidentally eaten something unpleasant. ‘My mother was not murdered,’ he said. ‘Dr Lambert lives down the road, he’ll tell you—’

‘He’ll tell us what you paid him to say twenty years ago,’ I interrupted. ‘That she died of mitral stenosis. But you know that’s not true. She was poisoned.’

‘I think you should be very careful what you say, Ms Ryeland.’

‘What? Or you’ll threaten me with those very expensive lawyers you’re always going on about? I think we’ve gone past that, Jonathan. And you can call me Susan, by the way.’ I was already on the edge of losing my temper. He had a way of making ‘Ms’ sound like an insult.

‘Well, I wish to place it on record that I never paid Dr Lambert a single penny—’

‘You need to be aware that Dr Lambert has made a statement in which he contradicts you, Mr Crace,’ Blakeney said, and I loved the deliberately cold and officious tone of his voice. ‘As a result of our inquiries, we have interviewed him under caution and he has admitted receiving a quite considerable sum of money from the estate to say that your mother died of natural causes, even though this was clearly not the case. You will be aware that we have requested an exhumation, which will be taking place later this month.’

Jonathan took the knock and tried to pretend it hadn’t hurt him. ‘That wasn’t me,’ he insisted. ‘If it happened, I knew nothing about it.’

‘I’m afraid he’s given a very different version of events, sir. He also has documentary evidence. The money was paid to him in the form of a cheque and it’s your name on the dotted line.’

I must admit it was delightful watching Jonathan squirm. A lot of the colour had left his face. ‘I was protecting my mother’s legacy,’ he said at length. ‘I did nothing wrong.’

‘That is not the case, sir. You were perverting the cause of justice—’

‘It was twenty years ago.’

‘But it was still a crime and it may well be that charges will be brought against you.’

‘How was I to know?’ Jonathan insisted. For a moment, he sounded almost tearful. ‘Her heart could have stopped at any time.’ He regained his composure. ‘Why would anyone want to kill her?’ he demanded.

‘If you’ll let me speak, I’ll tell you,’ I said.

‘All right.’ Jonathan slumped in his chair. ‘Get on with it, then.’

‘Do you have to be so rude?’ I wanted to ask him. ‘What have you ever done in your entire, miserable life that entitles you to talk to me like that?’

But I didn’t. Instead, I began.

‘You might like to know that your mother was almost certainly poisoned by arsenic,’ I said. ‘Her husband, Kenneth, had a lifelong interest in taxidermy. He was a taxidermist himself, but he also bought animals that had been killed and stuffed years before. You may not be aware of this, but taxidermists once used arsenic-based insecticidal soaps to clean the insides of dead animals. They say that if you pick up a specimen that’s more than fifty years old, you should always wear a mask and gloves. You can quite easily kill yourself and that is, in fact, what nearly happened: Kenneth became seriously ill. Dr Lambert described treating him for lesions and warts, which are both symptoms of arsenic poisoning, and he prescribed something called dimercaprol, which I’ve looked up on Google and it turns out it’s the classic cure. Speaking personally, I think taxidermy is disgusting, but the point is that anyone could have sneaked into Kenneth’s workshop and scratched enough arsenic out of a stuffed owl and a couple of hedgehogs to kill everyone in the building.’

‘Why am I here?’ Julia asked. ‘Why do I have to listen to this?’

‘Don’t you want to know who killed your grandmother, Julia?’ I asked her.

‘Not really. I’m just glad she’s dead.’

‘You’re here because you may have information that helps us, Miss Crace,’ Blakeney explained.

‘I don’t know anything.’

‘But you and your two brothers talked about killing Miriam,’ I reminded her. ‘You wanted to poison her.’

‘That was just a game. And we didn’t know anything about arsenic.’

‘That may be true. But after Eliot was caught trying to steal poison from Dr Lambert’s medicine bag, the entire house knew what you were thinking. And somebody realised that you’d given them a fantastic opportunity. They could poison Miriam with arsenic and, with a bit of luck, nobody would even notice. If they did, it was you children who would get the blame. Either way, they’d be in the clear.’

‘Why would anyone want to kill her?’ Roland asked. ‘Grandma was eighty-three years old. She was ill. She was going to die anyway.’

‘That’s the question everyone asked in your brother’s book,’ I said. ‘Why would anyone want to kill Lady Margaret Chalfont? But there was one person in this room who had every reason to kill Miriam.’ I turned on Jonathan Crace and rather enjoyed seeing him trying to avoid my eye. ‘She was threatening to sell the estate to American interests. I think you’d have happily killed her to prevent that.’

‘It was all words. She would never have done it.’

‘You say that now. Were you so sure of it then?’

‘Are you saying I killed my own mother so that I could take over her legacy?’

‘No, Jonathan. I’m just saying you could have. Just as Roland and Julia could have killed her to stop her taunting and teasing them. I know you like to pretend this isn’t true, but you know perfectly well that your mother was so vile that simply to meet her was a good enough reason to want to kill her – your lawyers probably hated her too.

‘But the actual reason Miriam Crace was murdered was very human, very understandable. It’s nothing that anyone has ever considered, but it’s been in front of us all the time.’

I turned to Julia.

‘I met your aunt Leylah for a drink and she said something very strange. It’s been on my mind ever since. She was telling me how everyone in the Crace family was a liar. Jonathan had lied about the death of his daughter. Gillian had lied to Eliot. And then she said: “ Freddy lied about his car accident – you should ask Julia what really happened .” I remember the exact words. So let me ask you now. In what way did he lie to you?’

‘What has my accident got to do with anything?’ Frederick interrupted. It was the first time he had spoken since he had sat down.

‘I don’t know what you want me to say,’ Julia complained.

‘Just tell me what happened.’

She answered before he could. ‘We were driving through west London. Uncle Fred – that was what I always called him – was taking me to the airport. We were in Kensington High Street and there was a red traffic light. I didn’t realise what was about to happen until it was too late. He drove straight through it and a lorry, crossing the junction, smashed into us. It hit the driver’s side of the car, which was why he was the one who was more injured. I got away with a broken collarbone and cuts and bruises.’

‘I told you about this,’ Frederick said. ‘I wasn’t concentrating. I had flu.’

‘No. That’s not true.’ Julia had finally answered my question. ‘I know that’s what you told everyone, but you weren’t ill. You were fine. You just weren’t looking where you were going. You didn’t see the light was red.’

Frederick stared at me balefully. ‘This happened a long, long time ago,’ he complained. ‘It was my fault and I was the only one who was badly hurt. Why bring it up now?’

‘Why did you lie?’

‘I didn’t! Well … maybe I did. I felt dreadful about what had happened. Julia broke her collarbone. She missed her flight. What was I meant to say? That I was asleep at the wheel?’

‘You could have told her you were colour-blind.’

Nobody spoke. Everyone was staring at Frederick.

‘Confusing red and green is one of the most common symptoms of colour blindness,’ I went on. ‘Drivers who are colour-blind have to be aware of the position of each light. They don’t think red, yellow, green. They think top, middle, bottom.’

‘So what? So what?’

‘Are you right-handed or left-handed, Frederick?’

‘Why do you want to know that?’

‘Please answer the question, sir,’ Blakeney cut in.

‘I’m left-handed,’ Frederick admitted.

‘I already know that,’ I said. ‘When you were at the party, you were holding a champagne glass in your left hand. Your right hand was in your pocket.’

‘My mother was left-handed.’ It was Jonathan who had spoken and it was the first useful thing he’d said.

‘I know that too,’ I went on. ‘When I was doing the tour of this house, I went into her office and saw her collection of twenty-three left-handed pens. She was also colour-blind. After Eliot went on Front Row , a journalist called Kate Greene wrote an article in the Daily Mail in which she mentioned that Karim and Njinga were both colour-blind, like their creator, Miriam Crace . You all know that being colour-blind and being left-handed are major genetic traits. Eliot told me that Frederick changed after his accident. He became angry and more distant. I think that was because he’d realised the truth.’ I paused. After everything I had been through, I wanted to enjoy the moment. ‘Miriam Crace was his mother.’

Both Jonathan and Roland Crace looked shocked. Julia was simply intrigued. Frederick had lowered his head, trying to hide his expression.

‘Frederick told me that he came to Marble Hall in 1961, when he was almost six years old,’ I said. ‘That means the year of his birth was 1955. He had spent the first five years of his life in the St Ambrose Orphanage and Children’s Home in Salisbury, which had Miriam Crace as its patron. He believed that his mother was a Traveller called Mary Turner and that his father was an itinerant worker – which would explain his mixed heritage. I imagine you’ve already checked that out, Frederick. You know it’s not true.’

Frederick didn’t reply.

‘The year 1955 was also an important one in Miriam’s life. That was when she came back from a six-month stay at a clinic in Lausanne, following a nervous breakdown caused by overwork. I think we’ve all guessed that there was no breakdown. There was an unofficial biography of Miriam written by a man called Sam Rees-Williams but never published. He claimed that she was promiscuous, that she had sexual affairs with both men and women and that this put her marriage under strain. He wrote that her visit to Lausanne was a trial separation from her husband, Kenneth, but he got that bit wrong. I think she was pregnant. Just like Alice Carling in Eliot’s book, she had a Roman Catholic background. She couldn’t have an abortion. It would have been unthinkable to have a child out of wedlock. So she gave birth to the child abroad and when she got home, she put him in her own orphanage and left him there for five years.’

‘Who was the father?’ Blakeney asked, but I think he already knew.

‘That’s a very good question,’ I said. ‘All along, I’ve been puzzled as to why Miriam, who seems to have been a world-class racist, adopted a mixed-race child at a time when attitudes were much more conservative than they are now. I asked Leylah about this. After all, Leylah had been the subject of racist abuse herself and there was that business with those two new characters in the books – Karim and Njinga. It was Leylah who told me about Miriam’s chauffeur, a Black man called Bruno. According to Leylah, Miriam adored him. She told me there was even a photograph of him on the piano – and the moment she said that, I should have twigged. I mean, he was her driver. Not her husband!

‘Unless, of course, he was also one of her lovers. This was 1955, let’s not forget. Miriam’s career was exploding. She was a married woman. When she gave birth to a mixed-race child, she must have believed that catastrophe was staring her in the face, that if she was found out, her rise to fame and fortune might be over. Why did Bruno leave? That’s what Eliot asked in the notes to his manuscript, and the answer is that Miriam couldn’t risk having him anywhere near her. She fired him or persuaded him to take a job elsewhere and then, once she’d got rid of him, she adopted their son and brought him to live in Marble Hall.

‘It’s a sad story. We have to look at it from Frederick’s point of view. His whole life has been an enigma. He’s never met his real father. He was adopted by this wonderful, famous author, but she never treated him like the rest of the family. He was given a room up in the attic and sent to the local state school. Miriam was his adoptive mother, but he wasn’t even allowed to call her that. Later on, he was packed off to accountancy school to become the family’s bookkeeper, and when that didn’t work out, he was sent back to Marble Hall to be a glorified tour guide. Eliot called him a second-class citizen and that’s exactly what he’s always been.

‘Do you think Frederick never wondered why he was being treated like that? Do you think he never asked himself why he was so different? Well, the answer came after his car accident. He already knew he was left-handed. Now he realised he was colour-blind.

‘Just like Miriam.’

Frederick looked up. He’d had enough. I saw that at once. He just wanted this to be over.

‘It was after the accident that I started asking questions,’ he said. ‘And you’re right, Susan. It was easy to discover that Mary Turner had never existed and that my documents at the orphanage had been falsified. Then I made the connection with Lausanne. It was a prenatal clinic – nothing to do with stress or mental health. But, you know, I didn’t need proof. I think, in my heart, I’d always known. A son will always recognise his mother even when that mother has lied to him every single day of his life.’

He drew a hand over his one good eye, fighting for control.

‘My first thought was to tell the world what I’d found out, what a devil she was, what a monster. I knew all about the sex scandals too. Kenneth Rivers told me. He was my one friend in that house and I think he half suspected the truth about me. Maybe he saw something of her in me. I could have brought her down that way too – but what good would that have done me? I’d have lost everything. The family would have rejected me. And if I destroyed her reputation, we’d lose the money too … the books, the Little People! What would you have done if you’d been me? She sent my father away! She made sure I never met him and he never found out I existed. I finally managed to track him down, but I was too late. He was dead. He died on his own, in poverty. She ruined his life the same way she ruined mine.

‘I knew I had to kill her. She was dying anyway, but I wouldn’t be able to live with myself if I didn’t pay her back. A mother … doing what she did to her own flesh and blood? I’d have loved to have strangled her. I’d have loved to have cut her throat. I thought about smothering her in her bed. But when I heard about the grandchildren and Eliot stealing medicine from Dr Lambert, that was when I knew it had to be poison. At the end of the day, I didn’t care how she died so long as it was by my hand.

‘So … you’re right. I used arsenic that I scratched out of the feathers of one of the birds that Kenneth had bought as part of his collection. It was a kingfisher in a glass case. We’d always been told that we must never touch it and once I’d cut it open, I soon found out why. Of course, I couldn’t be sure if it would work, but if it didn’t, I’d try again.

‘I didn’t need to worry. It worked first time. You know, I think it was the only time in all the years I spent at Marble Hall that I felt complete. I had to laugh when Jonathan bribed Dr Lambert to issue a false death certificate. Natural causes! He was so scared that the truth about that bitch would come out that he helped cover up her murder.’

‘You also killed Eliot Crace,’ Blakeney said.

Frederick nodded. ‘I was sorry about that. It wasn’t something I wanted to do. But I had no choice.’

‘You made a mistake,’ I said. ‘At the party, Eliot shouted to everyone that he knew who had killed his grandmother and that he had seen them go into her bedroom. He said he could see them right there, at the party. But he wasn’t talking about you, Frederick. He was talking about his brother, Roland. Still you followed him out. You had a car. You ran him down.’

‘It was his own fault. He shouldn’t have boasted like that.’

‘He wasn’t boasting, Frederick. He was in pain. Like you.’

Frederick shrugged. ‘I had to stop him talking. What else was I meant to do?’

Jonathan, Roland and Julia were frozen, unable to take in what had just occurred. In their different ways, all three of them had played a part in the events that had led to Eliot’s death. Blakeney and Wardlaw got up and closed in on Frederick.

‘You’re going to have to come with us.’ Wardlaw put a hand on his arm.

But I couldn’t leave it there. ‘I am so very sorry, Frederick,’ I said. ‘You were treated horribly and I can try to understand what you did when it comes to your mother. But Eliot was never a part of it. He was a victim as much as you. And killing him was unforgivable.’

‘You’re right, Susan.’ Frederick Turner looked at me with the saddest smile I’d ever seen on a man. ‘But you know what? I don’t think he was so happy being alive. Maybe I did him a favour.’

They led him away. I watched them go. Then, without saying anything to anyone in the room, I followed him out. I wasn’t sure how I was going to get back to London, but I didn’t care. I just wanted to get into the fresh air and walk away.

It was finally over. I’d named the true killer and closed the investigation, but right then I felt only sadness. Two lives taken but so many more lives destroyed. That was the legacy of Marble Hall.