The young man took his order willingly, and walked across the grass to meet her. He carried his own shopping bags like a servant at a task.

Hobbes felt a sudden panic. ‘Esme, wait!’ But she would say no more. He watched them walk away, more worried than ever about his son. But he made no attempt to follow, knowing full well Esme’s fear of being seen too close to home with the enemy, a cop.

Boy and girl, neither glanced back.

Hobbes looked at the page with his telephone number scrawled in it. He screwed it up and threw it into the gutter. Useless. Bloody useless! He went back to where his car was parked and sat in the driver’s seat for five minutes, thinking over the conversation. He stared at the photograph, willing it to give up its secrets. The woman’s left arm was stretched out to show off the markings on her hand, the blue at the end of each finger. And that smile in place, that was the worst thing, as though the sickness meant nothing at all to her. She revelled in it. And her right arm around Martin’s shoulders, the clutch of possession.

Hobbes felt his anger rising.

In the Dark

Deptford marked the south-eastern boundary of old working-class London, before the greener plains and townhouses of Greenwich and Blackheath took over. Here the old terraced houses and workshops still existed, and the air was gritty and grey. Rain speckled the windscreen, first a few drops and then a downpour. He had to lean forward in his seat to peer out through the always disappearing arcs of clear glass left by the wipers.

It was good: the rain, the need to concentrate, to locate the address that DS Latimer had given him. It stopped him brooding too much.

There it was – 37 Parchment Street. He pulled up at the kerb and waited for a moment, hoping the downpour would let off a little. It didn’t. He lodged the cardboard folder under his jacket and got out of the car. Even walking at speed, he was drenched in seconds. It took a while for the bell to be answered, and he was on the verge of walking away when the front door opened.

‘Mrs Fairfax?’

‘That’s right. I was just getting ready to—’

‘I’m Detective Inspector Hobbes. I’m here to see your son, Thomas.’

‘You’re going to arrest him, are you? About time!’

‘No. Not at all. I just want to—’

‘I’m joking!’ The door opened fully. ‘Well, come in then! Hurry up – you’re getting my hall carpet wet.’

Hobbes tried to remember her name. Had DC Fairfax ever mentioned it?

He followed her into the hallway. Mrs Fairfax was dressed to the nines in a fancy red dress and a fake-fur stole. A string of pearls circled her neck and her face was done up in rouge and lipstick. It was two in the afternoon. ‘It’s my day off,’ she said, in answer to his look.