Keith Li lifted his machete and there was a moment of total stillness in the room as he brought it down on Troy’s arm at its thinnest point, removing the hand and perhaps three inches of wrist from the arm where the radial artery rises close to the surface.

It is exactly where you take a pulse, looking for signs of life, and now a bright arterial spurt of blood announced the end of a life, and Troy’s scream seemed more of shock than pain.

Then I was scrambling away from the severed hand that had fallen inside the tub, unable to breathe, so much blood still flowing, looking at Troy’s body twitching on the floor with his final scream still ringing in my ears. Keith Li had the girl in the wedding dress in his arms. The other Chinese men were already leaving, the younger one dragging the dreadlocked goon by his feet, still groaning, and the older one hefting Troy’s lifeless body and throwing it across one of his shoulders.

Keith Li followed them, whispering something to the girl in the wedding dress, until my voice called him back.

‘Don’t go,’ I said, desperately pulling on my clothes. ‘There are other people who need your help.’

Keith Li shook his head. He didn’t even turn to look at me.

‘I told you,’ he said. ‘We look after our own.’ A pause. ‘Now perhaps you will believe me.’

‘Keith, please – there’s a woman who needs help out there.’

But he was gone.

I was expecting to find a war zone in the drawing room. But beyond the front door hanging from its hinges and a frosting of broken glass over the thick carpet, the room was untouched apart from a chair that appeared to have been broken over someone’s head.

But everyone was gone.

I searched the bedrooms.

They were all exactly like the room I had left, these bleak little sex cells with a large shallow bathtub and a single bed. Rooms to seal the deal. In the room at the very end of the corridor I found Edie Wren bending over Rabia Demir. She was not moving.

‘I just called it in on the landline,’ Edie said. ‘But I think it’s already too late.’

‘What’s wrong with her?’

‘The women in here are on a diet of Rohypnol,’ Edie said. ‘But they’re been experimenting with Rabia. She’s on something more powerful than Roofies.’

‘Fentanyl,’ I said.

Edie nodded.

‘And it’s killing her, Max.’

Fentanyl is one hundred times more powerful than pure, pharmacy-grade heroin. Fifty times more powerful than morphine. It is a painkiller so powerful that it can kill you without you caring very much. It is often called the most powerful drug in the world.

‘Where are our people?’ I said.

‘Someone jammed the penthouse lift. They’re using the stairs.’

‘Fifty floors? The stairs are not going to be fast enough.’