The Anne bobbed gently in the current, moored beneath overhanging myrtle beech branches that offered a sense of privacy. Its sides green with mould and decay, the converted ferry had the charm of all things rustic and abandoned. A rickety wooden pier led from the open doorway up to the Dempseys’ empty block of land.

As far as ice labs went, it wasn’t the most secure – it was clearly visible to any traffic on the river – but who would want to snoop on a houseboat? Still, while Shelby set up her equipment, Mackenzie had spent his time installing heavy curtains and new deadbolts on all the doors just in case.

He turned back from the ocean and pulled on the pink coveralls and face mask that Shelby had left for him. The mask smelled like new plastic, and the eye-guard immediately fogged up. He unbolted the outer door, stepped through and locked it again from the inside before heading down into the lab. A solid bar of tension sat between his shoulder blades. There was no going back now if they were caught.

But also . . . he was excited. Since Ahab’s boat, all those other feelings were still there, the worry about getting caught and the fear for Shelby, but . . . they were lessened, somehow. He felt confident. He could give himself permission to be excited about how this might turn out. He’d done this many times before – there was something about it that brought you face to face with your humanity.

Shelby stood in front of the lab she had created, which had once been the houseboat’s dining room; it wasn’t the biggest room in the place, but the range hood provided good ventilation without raising any suspicion.

She was clad in her own coveralls, hair safely tied back into her hood. On the table before her were beakers, vials, tubes and Bunsen burners. The boxes of Sudafed were lined up against the wall, alongside bottles of powders and liquids labelled in Shelby’s careful handwriting.

Mackenzie stepped up beside her. ‘You ready for this?’

‘Easy as pie.’

‘There’s no going back,’ he said.

‘I know!’ she snapped. ‘But I’m making it as pure as possible. Then it won’t hurt people as much.’

‘It’s still gonna hurt people,’ said Mackenzie. He’d seen firsthand the desperation of those willing to do anything for another score. Hell, he’d been one of them.

‘Ice only hurts people because of the acidic nature. If you can get the pH levels right, it doesn’t eat away at the body,’ she said crisply.

‘Chances are that eventually they’ll put enough through themselves that sooner or later the acid eats part of their flesh. They’re not always going to be using your stuff, Shelby. If they go long enough, they all end up looking like skeletons. Besides, it’s not the acid that hurts them, it’s the sleep deprivation.’