He already knew they had a promising lead: Forrester had rang four days back saying they now reckoned the gang was possibly somewhere around Montpelier House, south of Dublin. The home of the Irish Hellfire Club. The detective had explained Scotland Yard’s route to this conclusion: how the killers were surely moving in and out of the country, because of their ability to totally disappear, yet they weren’t being traced by Customs and passport checks. That meant they must be escaping to the one foreign country for which you didn’t need passport checks-when leaving the UK.

They must have driven or flown to Ireland.

All that was very plausible. But Forrester had felt it necessary, when talking to Rob, to add some strange supporting theory-about buried victims and the Ribemont death-pit and Catalhoyuk and a murderer called Gacy, and the fact that Cloncurry would choose somewhere near his ancestors’ victims…And Rob had switched off at that point.

He was far from convinced that Forrester was right with these psychological speculations. It just seemed to be a hunch and Rob didn’t trust hunches. He didn’t trust anyone. He didn’t trust himself. The only thing he could trust was the sincerity of his own self-loathing, and the fierceness of his anguish.

That night he went to bed and slept for three hours. He dreamed of a crucified animal, screaming on a cross, a pig or a dog maybe. When he woke it was dawn. The image of the nailed animal persisted in his mind. He took some Valium. When he woke again it was noon. His mobile phone was ringing. Ringing! He ran to the table and picked up.

‘Hello? Hello.’

‘Rob.’

It was…Isobel. Rob felt his mood dive precipitously; he liked and admired Isobel, he craved her wisdom and succour, but right now he just wanted to hear from the police, the police, the police.

‘Isobel…’

‘No news then?’

He exhaled. ‘Not since last time, no. Nothing. Just…just these fucking emails. From Cloncurry. The videos…’

‘Robert, I’m sorry. I’m so sorry. But…’ She paused. Rob could picture her in her gracious wooden house, staring at the blue Turkish sea. The mental image was piercing, reminding Rob of how he and Christine had fallen in love. There, under the Marmara stars.

‘Robert, I have an idea.’

‘Uhn.’

‘About the Black Book.’

‘OK…’ He could barely muster any interest.

Isobel was not dissuaded. ‘Listen, Rob. The Book. That’s what these bastards are looking for, right? The Black Book? They are absolutely desperate. And you’ve told them you can find it, or you’ve found it, or whatever, to keep them going…Correct?’

‘Yes, but…Isobel we haven’t got it. We have no idea where it is.’

‘But that’s it! Imagine if we do find it. If we do locate the Black Book then we’ve got some real leverage over them, haven’t we? We can…swap…negotiate…you see my meaning?’

Rob assented gruffly. He wanted to be energized and excited by this phone call. But he felt so tired.

Isobel talked on. As she did, Rob wandered barefoot through the flat, cradling the phone under his chin. Then he sat at his desk and gazed at the shining laptop. There was no email from Cloncurry. No new email, at least.

Isobel was still talking; Rob tried to focus. ‘Isobel, I’m not with you. Sorry. Say again?’

‘Of course…’ She sighed. ‘Let me explain. I think they-the gang-might be barking up the wrong tree. Vis à vis the book.’

‘Why?’

‘I’ve been doing some research. We know, at one point, the gang were interested in Layard. The Assyriologist, who met the Yezidi. Correct?’

A dim memory wafted across Rob’s distractions. ’The break-in, at the school, you mean?’

‘Yes.’ Isobel’s voice was crisp now. ‘Austen Henry Layard, who instigated the Nineveh Porch. At Canford School. He is famous for meeting the Yezidi. In 1847.’

‘OK…we know that…’

‘But the truth is he met them twice! He met them again in 1850.’

‘Rrright…so…’

‘It’s all in this book I’ve got-I’ve only just remembered. Here. The Conquest of Assyria. Here’s what it says: Layard went to Lalesh in 1847. As we know. Then he returned to Constantinople and there he met the British ambassador to the Sublime Porte.’

‘Sublime…’

‘Porte. The Ottoman Empire. The ambassador was called Sir Stratford Canning. And that’s when it all changes. Two years later, Layard goes back to the Yezidi again-and this time is met with inexplicable triumph, and he finds all the antiquities that made him famous. And all this is true. It’s in the history books. So you see…?’

Rob forced the image of his daughter from his mind. The leather gags…’Actually, no, I haven’t the foggiest what you’re on about.’

‘OK, Rob, I’m sorry. I’ll get right to the point. On his first expedition Layard went to Lalesh. My guess is that when he was there he was told by the Yezidi about the Black Book, how it had been taken from them by an Englishman, Jerusalem Whaley Layard was the first Brit the Yezidi had met, probably the first westerner-since Whaley’s visit-so it makes perfect sense. They must have told him they wanted the Book returned.’

‘Mmmmaybe…’

‘So, Layard then goes to Constantinople and tells the ambassador, Canning, about his findings. We certainly know they met. And we also know Sir Stratford Canning was Anglo-Irish, of the Protestant ascendancy.’

Rob dimly discerned, at last, where this might be going. ‘Canning was Irish?’

‘Yes! The Anglo-Irish aristocracy. A tiny coterie. People like Whaley and Lord Saint Leger. The Hellfires. They are all related.’

‘Well yes, that’s curious. I s’pose. But how does it all fit in?’

‘Around the same time, rumours were flying around Ireland, about a certain Edward Hincks.’

‘Sorry? Right over my head.’

‘Hincks was an obscure Irish parson from Cork. Who single-handedly managed to decipher cuneiform! All this is true, Rob. Google it. This is one of the great mysteries of Assyriology. The whole of educated Europe was trying to decipher cuneiform, then this rural Irish vicar beats them to it.’ Isobel was rushing her words in her enthusiasm. ’So let’s put two and two together. How did Hincks suddenly decipher cuneiform? He was an obscure Protestant cleric from the middle of nowhere. The bogs of Eire.’

‘You think he found the Book?’

‘I think Hincks found the Black Book. The book was almost certainly written in cuneiform-so Hincks must have somehow found it, in Ireland, and translated it, and deciphered cuneiform, and realized he’d found the Whaley treasure. The famous text of the Yezidi, once owned by the Hellfires. Maybe he tried to keep it secret-only a few Protestant Irish toffs would have known what Hincks had found, people already aware of the Whaley story, and the Irish Hellfires, in the first place.’

‘You mean Irish aristos. People like…Canning?

Isobel almost yelped. ‘That’s it, Rob. Sir Stratford Canning was hugely important in Anglo-Irish circles. Like many of his type he was no doubt ashamed of the Hellfire past. So when he heard that Whaley’s book had been found Canning had the perfect idea to solve all their problems. They wanted rid of the Book. And he knew that Layard needed the Book to give to the Yezidi. And Hincks had just found the Book.’

‘So the Black Book was sent back to Constantinople…’

‘And then finally it was returned to the Yezidi…via Austen Layard!’

The phone went silent. Rob pondered the concept. He tried not to think about his daughter. ‘Well. It’s a theory…’

‘It’s more than a theory, Rob. Listen to this!’ Rob could hear the pages of a book being flipped. ’Here. Listen. Here’s the actual account of Layard’s second visit to the Yezidi. “When it was rumoured among the Yezidi that Layard was back in Constantinople, it was decided to send four Yezidi priests and a chief”-and they went all the way to Constantinople.’

‘So-’

‘There’s more. After some “secret negotiations” with Layard and Canning in the Ottoman capital, Layard and the Yezidi then headed east into Kurdistan, back to the lands of the Yezidi.’ Isobel drew breath, then quoted directly: ‘“The journey from Lake Van to Mosul became a triumphal procession…Warm feelings of gratitude poured over Layard. It was to him the Yezidi had turned and he had proven worthy of their confidence.” After that the group made their way through the Yezidi villages, to Urfa, accompanied by “hundreds of singing and shouting people”.’