He reached the crossroads, rained ammunition down the right-hand corridor, and continued his charge against the desperate wishes of his ageing body. Lorraine had muttered something about a Special Weapons Storage Facility next to the curve in the path, and McCormick was keen to find a weapon that would speed up his job. He pulled open the door and shot a bullet into the room’s single occupant.

McCormick tore through the wooden crates before him, and scowled in disgust at the range of advanced weaponry. Cluster-rocket launchers. Napalm mines. And a box which read ‘Acid grenades: for use on civilians’.

He stuffed his pockets with acid grenades, for the inevitable moment his bullets would run dry, and then found a weapon that fitted his needs perfectly.

The hand warhead. Iain Marshall’s nifty name for a handheld weapon the shape and size of a traditional hand grenade, but filled with NPN8. Its warning label included, bold and capitalised, ‘NEVER USE WITHOUT A FULL SURROUND OF SHELTER’, suggesting that its blast radius would reach further than it could be thrown. McCormick took two in his left hand and a third in his teeth, leaving his heavy assault rifle in the grip of four tired fingers.

He burst back into the corridors and ran to the next crossroads, gunning down another clone as he ran to his right. Two left turns later, having followed Shannon’s instructions to perfection, he found himself one door away from the final resting place of Nathaniel Pearce’s hallowed research.

McCormick jerked open the door to the data servers and found a thin chamber the length of a train carriage, filled from front to back with caged hard drives and enough flickering lights to fill a disco. The heat was intense; even the groaning fans that lined the ceiling were locked in a constant battle against the temperature of the computers.

Someone opened fire from down the path. McCormick sheltered behind the open door, and decided enough was enough. One of those bullets could have killed him stone dead, and wiped out any chance of him fulfilling his mission. He couldn’t afford to die, not when he was so close to destroying their fourth target out of five.

Are we really that close to surviving the night? I honestly thought we’d be dead before we got three .

McCormick shook his head and took a deep breath. The sooner he did this, the better.

He pulled the pin on the first hand warhead, and launched it to the far end of the chamber. He aimed the second at the halfway spot on the metal floor, and sent the final one a distance he thought he might just survive from. He took his rifle in both hands, leapt back into the open corridor, and killed a clone who had not thought an old man could jump so fast.