Luke felt a surge of adrenalin course through him. This was what he’d come here to do: confront Hugo Squires and finish this once and for all. A voice in his head was telling him to hang back, use his phone to call for back-up, wait for reinforcements and surround the locomotive with so many people Squires would have no hope of escape. But that wasn’t his way. Fuck it, he thought, let’s do this. He slipped beneath the engine, bending himself double in the cramped space, and flicked on the torch once more. Crouching and peering, he probed the darkness. Nothing. And then he heard it again, the unmistakable sound of a boot moving against stones. Someone was shifting their weight and they were right behind him.

Every muscle in his body was tensed for action as Luke half turned to face the source of the noise. In that moment he felt a searing pain lance into his thigh. Crying out, he staggered back, twisting round to shine the torch on his assailant. There, lit up in the white beam, was the crouching figure of Hugo Squires. His eyes were wild and staring, his face and arms blackened with engine dirt, and in his right hand he brandished a penknife that glinted wetly with Luke’s blood. But it was what he was holding in his left hand that terrified Luke. It was a silver canister with a timer attached.

Luke gritted his teeth against the pain as he felt the blood seeping down his leg. But he willed himself to block it out. Focus, Carlton, you need to finish this. He called into the dark, ‘Give it up, Squires. It’s over.’

No reply, just heavy breathing. Suddenly Squires lashed out again. Luke saw the glint of the blade and recoiled just in time. He let go of the torch and shot out his left hand, grabbing a fistful of dirt and stones. In one fluid movement he flung them into his opponent’s face. Momentarily blinded, Squires howled and Luke made his move. He reached out in the dark to locate Squires’s leg with one hand and slammed the stone down hard on his kneecap with the other. There was a sickening crunch as the bone shattered and Squires let out a high-pitched scream, dropping both the knife and the canister. Luke sprang forward, his own pain forgotten, his arm poised to slam home the pointed stone once more, this time into the man’s skull. Everything Luke had been through with this mission boiled down to this supercharged moment as he held a human life in his hand.

And then, suddenly, there were lights and shouts and shadows and figures running. ‘Armed police!’ he heard someone yell.