‘A fungus of some kind. Like the one we found on the dead dog in the park.’

‘OK. What do you need?’

‘I want to know what it is. Species, habitat, effects on the psyche. The lot.’

The two men went their separate ways. Hobbes climbed the stairs to the second floor. His desk was covered with papers. He was searching through the top few sheets, hoping there was something of interest, when Latimer appeared at his side.

‘Meg, no more arguments. Please.’

Her face was set, cold. ‘Actually, this just came in.’ She handed over a folder. ‘Report from St Catherine’s House. I asked them to look for birth certificates for anyone called Adeline Graves, within a reasonable set of dates. And this is what they found.’

It was a copy of a birth certificate. Hobbes read off the entries.

‘Date and place of birth: Third November 1936. Richmond. Name: Adeline.’

Latimer allowed herself a little smile. ‘There she is. Finally.’

He nodded. ‘A girl. Father is … Leonard Albert Graves. Mum is Mary Estelle Graves, formerly Layne. Father’s occupation: Author. Nothing listed for Mary Estelle.’

‘They didn’t bother with the mother’s occupation back then.’

‘Right. And Informant?’

‘That’s the person who provided the information for the certificate.’

‘Listed as Leonard Graves.’ He waved the sheet of paper around. ‘So there was a fourth child. Excellent.’

‘We’re getting somewhere.’

‘Is there a death certificate, by any chance?’

‘I have an officer working on that. But nothing up to now.’

Hobbes looked again at the details of the birth: ‘1936, November. So if she’s alive, Adeline would be what now … mid-forties?’

‘Forty-four. With a birthday coming up.’

‘Good. This is excellent. A few more details, and we can start to—’

‘If she’s alive.’

Hobbes was adamant. ‘Until I find a body, she’s alive. That’s the rule.’

Latimer nodded. ‘I’m calling it a day. I’ll try Rosamund Kepple in the morning.’

‘Yes. Thank you, Meg.’

His mind had already moved on. He read again each element of the birth certificate, as though any one of them might hold the secret, the key. His eyes were irritated, and a dull pain took over the exact centre of his skull. That’s how it felt – a very particular pain, in a very particular place: targeted.

The telephone on his desk rang. It sounded like a klaxon.

‘Yes?’

‘Oh.’ A woman’s voice, anguished. ‘Is that …?’

‘Who is this?’

‘Inspector Hobbes, is that you?’

‘What do you want?’ He rubbed at his brow, pressing hard with his fingertips.

‘It’s Delia. You know …’

‘Tommy’s mother?’ He felt a tightness in his chest, awaiting bad news. It was always the same with Fairfax. ‘What’s wrong? Is Tommy all right?’

‘Can you come round, Inspector? Do you have time?’

‘Of course. What is it?’

‘Please. Just come round.’

He drove east, to Deptford. The rain kept off for a while, and the streets were packed. He had to concentrate all his focus on the road ahead, trying to avoid the haze that sometimes descended. The pain in his head had lightened, a little. But his eyes ran with tears.