But Manning was oblivious to protocol. She continued to stare at the cell as she gave her distracted answer: ‘Prisoner Zero.’ Hal was not enough of a neophyte to probe further.

‘Tell the General we’ll both be around for the interrogation,’ Reid said to Hal. ‘We’ll do it in four-one-four — there’s a two-way mirror.’

‘Got it.’

As Hal turned to retrace his steps, a disturbance broke out just ahead. A guard staggered backwards out of an open cell door, his SA80 spraying bullets all around. He was wearing an ABC isolation suit, a red arterial spray gushing from a ragged tear down the front of it.

Suddenly the corridor was filled with the most terrible sounds: jungle shrieks, haunted moans, insectile chittering and a low, chilling susurration. The prisoners had smelled the blood.

Hal was rooted by the sight for a second too long. Just as he was about to run back up the corridor, a small black shape bounded from the cell on to the chest of the still-twitching guard. At first, Hal thought it was a spider the size of a small dog, then some kind of lizard. Finally, he realised he was looking at an imp that would not have been out of place in a medieval wood-carving. It was the glossy black of crude oil and covered in gleaming scales. Its body had human proportions, but its head was oversized, like a baby’s. A pointed tail lashed back and forth.

‘Take that,’ the devil said with a swipe of razor-sharp talons, ‘for presumption. And that for stupidity. And this simply because it is my nature.’ The talons became a blur of rending and tearing.

And then the imp stopped, sniffed the air and turned its head in an oddly mechanical way towards Hal. Hal’s blood ran cold as the devil’s red eyes fell on him.

‘Aha!’ the imp said with jubilation. It sounded like a throaty old man. ‘Fresh meat.’

It leaped from the seeping corpse so fast that Hal couldn’t keep it in his vision. Bouncing off the walls and ceiling, it hit Hal full force in the stomach. He fell to the floor, winded, as the imp did a little mocking dance around him. Before Hal could lever himself up, the devil jumped to squat on his chest with surprising weight.