For a security company, Ellison's security was pretty lax. One swipe of the skeleton card and I was in. Then it was time to test the device in my hand. I pointed it upwards and hit the button. I'd soon know if it worked.

I made my way to the filing room, digging out the plans for the tower and committing them to memory. I was still thinking about it when I left. I hit the button again on the way out. It seemed to have worked. No alarms had gone off, none of the cameras had tracked my movement. I'd have to thank George if I got out of this alive.

The layout of the tower. Positions of alarms, sensors, cameras. I took them from the flat blueprint into a three dimensional model in my head, working out the best way to do things so that I had the best possible chance when I got there.

I went to the building opposite first, climbing up to the roof via the outside fire escape. It was a long climb but I didn't stop until I reached the top. Once there, I laid down at the edge and looked across, using George's telescope to peer over the low wall and beyond. It was heat sensitive, the internal screen replacing a lens. On it I could see the positioning of everyone in the building, a blur of heat until I zoomed in to the top floor. Only one person pacing, clearly a guard, following the same range of movement around the floor space, going from room to room.

On the floor below I found what I was looking for. There she was. Emotions started to bubble up as I matched her positioning with the map in my head. She was in a cupboard. Slumped on the floor. Was she drugged? Dead? No, there wouldn't be that much heat if she was dead. "I'm coming for you," I muttered out loud as I tracked the other people on the floor. He was there.

I got lucky when I returned to the ground. I was watching the tower, trying to decide the best way to get inside. The door opened and out came someone I recognised. It took a moment to place him. He'd aged too, his gut more prominent than Sharp's. It was Louis, the man who'd sold her to him.

He'd clearly been demoted at some point. He had a security guard uniform on and he looked miserable. I watched as he crossed the street and headed straight into the nearest bar. I followed.

He was already halfway down his pint by the time I got inside. I sat in the darkest corner and waited. The rate he was drinking, it wouldn't be long. I was right.

Five minutes later, he stood up and headed into the toilet. I followed. Two minutes later, I came out with his I.D. I'd left his body in one of the cubicles, Out of Order sign stuck on the door and he was good in there for a while. By the time they found him, I'd either be dead as well or long gone.

The skeleton swipecard might have got me in the building but for what I had planned, this would work so much better.

I hotwired a car a couple of streets away, driving it over to the parking garage under the tower. The security guard on the door took one look at the I.D and then waved me through. Piece of cake.

I parked up by the vent I needed. The car blocked anyone from seeing as I pulled the grille off the vent and climbed inside. The plans showed this led up to the second floor. I crawled through, changing as I went. I stepped out in overalls with my ear glued to a phone. "Three of them and their nest," I said. "We need a bigger batch if we're going to get them all."

The few people who'd seen me emerge looked away. I continued talking loudly about rats until I got to the stairwell. Once the door was closed behind me, I hit the button on George's device. Cameras should be off. Sensors should be shut down. I wouldn't have long. The battery on the device didn't last forever. I needed to move quickly.

The battery lasted until I got to the top floor. I heard it fail with a ping sound and then the camera above my head began to move. I darted through the door and into the corridor beyond.

I used the telescope to pinpoint the guard, knocking on the door just as he walked past. He pulled the door open and as he did so, I got my hand to his neck, catching it at the right angle to yank him off his feet and over my shoulder. He landed with a crunch.

I used the telescope again as I walked around the floor, waiting until I was directly above her. I looked around me. The vent on the blueprint wasn't there. Now what?

Through the telescope, I could see someone was approaching the cupboard. I needed to move fast. I crossed to the nearest window, pulling it open and stepping out onto the balcony, the wind hitting me at once.

Swinging my legs over, I didn't look down. I just jumped, landing on the balcony below with a thud. I was in front of the window I'd fallen from last time. This time, I was going in, not coming out. I stood up, tapping on the glass and getting the attention of the guards.

They started to shoot at once. I was ready, leaping over the side, grabbing the railings and hanging down. I waited. Someone would get curious eventually. Hanging in the air, I could hear the Thames below, even with my ears ringing from their shots. The glass was covered in a spiderweb of cracks and when someone pushed it open to check, I lifted myself upwards quietly. As they leaned out, I grabbed them, sending them flying through the air, their scream fading away as they fell down to the river.

I got through the window before it could be closed, my gun at the ready. I fired until I was empty then moved onto the remaining men.

"Stop there," a voice boomed and the guards paused, looking behind them. I saw what they saw. Mr Sharp was holding a gun to Rebecca's head. She was wild eyed with fear as he gripped her tightly around the neck. "Drop it," he said, motioning towards the gun.