Cat-like, he crept up slowly to the door of the first of them. All his senses felt on edge, as if primed for this moment. It was hard to believe that only yesterday afternoon – yesterday! – he had been put through his paces on that hostage-rescue simulation course back in the UK. It just showed you never knew when you were going to need the training to kick in. He slowly turned the handle of the door. It was locked. He looked around for something to wrench it open. Nothing. He tried the second door and this one opened with a rusty rasp. He stepped quickly inside and waited, listening. Was he being watched? He didn’t think so. There was nothing but the mournful whistle of the Arctic wind outside.

He took out his phone and pressed the torch function, squinting as he adjusted his eyes to the sudden flood of light. Ahead of him, inside the room, he could see a long steel desk, several chairs scattered around haphazardly and a lamp lying on its side. The place looked as if someone had left in a hurry. Luke walked over to the desk, then opened the first drawer. Empty, except for some unused SIM cards, still in their sealed wrappers. He opened the second drawer: empty, and the third. He was about to leave when he saw something at his feet: a box file, spilling its contents across the floor, clearly dropped by someone in a rush. Luke scooped the papers up and shone the phone torch on them. All in Cyrillic. Russian documents. Well, that didn’t prove anything, but he wasn’t going to pass them up. He folded them in half and stuffed them into the inner pocket of his jacket for later. It was time to move on and check out the third room.

What he saw when he stepped through the door stopped him dead in his tracks. Everything before him, lit up by his phone torch, was covered with sheets of polythene, from floor to walls to ceiling. In a corner there was a line of blue plastic containers, and a faint chemical smell hung in the air. He decided it was safest to touch nothing and instead he reached for his surgical mask, still folded in his pocket, and placed it over his mouth and nose. Probably a bit late for that, he realized, but he wouldn’t hang around. He took in the scene: this had to be some sort of makeshift laboratory. Luke shot a few seconds of video with his phone and was about to take some stills when he thought he heard a shout. He listened again. Yes. There it was: Kristian was calling from inside the main building.

‘Luke! Come quick!’ He sounded scared.