'These stairs go to the catacombs,' Samuel said. He was emptying his revolver of bullets that glowed with a faint blue light of magic within their glass casings. He put them into a pouch on his utility belt, and then produced eight regular slugs from a separate pouch. 'Can you sense anything down there, Clara?'

As Samuel reloaded his gun, Clara stuck her head out into the stairwell, trying to ignore the thud of her heart in her ears as she listened.

'I can hear ... it sounds like a child humming.' She sniffed the air, and then swallowed heavily. 'Someone's bleeding down there.'

'Give me the satchel,' Samuel said, holstering his revolver.

She passed him the satchel, and he took out two of the spell spheres, holding one in each hand as if weighing them.

'Keep still,' he said, and then broke a sphere against Clara's chest with a tinkle of glass.

She gasped as a shock ran through her body.

Samuel then broke the second sphere against his own chest. He then faded slowly and disappeared. Clara looked down, but could not see her hands or body or legs ...

'We're invisible,' she said in awe.

'Illusion,' Samuel's disembodied voice explained. 'It'll fool the Orphan, but not for long. We have to move quickly.'

Clara felt him take her hand, and he pulled her through the door. They crept down the darkened stairwell. It seemed to take a long time to reach the bottom, where they came to an archway that led into the catacombs.

Candles burned everywhere, at least a hundred of them, of varying thickness and length. They flickered in dark niches between tombs, upon mantles and statues, dripping hot wax down stony faces onto the dusty floor. On the far wall hung an old tapestry, once a monument to someone, now faded and torn.

At the centre of the room, side on to the archway, Charlie Hemlock was hanging by his wrists from a rope. The rope was threaded through a ceiling pulley and secured to a metal ring on the floor. It creaked as Hemlock's body swayed gently. His eyes were closed, his expression was vapid. His face was smeared with blood that also stained the front of his clothes. His lips were split and swollen; Clara's fingernail marks scored his cheek, and it looked as though a blade had been taken to his forehead.

A thin metal tube had been inserted into each of Hemlock's legs, just above the ankles. His blood dripped from them, slapping wetly into a small copper cauldron. And before the cauldron a child sat cross-legged, rocking back and forth as it hummed something akin to a nursery rhyme.

Samuel gave Clara's hand a reassuring squeeze before he released it.

She found it hard to believe that it was a wild demon from the Retrospective that had Hemlock at its mercy. The Orphan appeared to be a young boy of nine or ten years old; its limbs and body were thin, its belly slightly bloated, and golden curls crowned its head.

Samuel pressed the hilt of a knife into Clara's hand, and his lips brushed her ear as he whispered, 'I'll deal with the Orphan. As soon as it's distracted, you cut Hemlock free and get out as fast as you can. Don't wait for me. Don't look back.'

Clara nodded, though it was impossible for Samuel to see the gesture. She heard the faint chink of glass on glass and knew that Samuel was retrieving more spell spheres from the satchel.

The demon stopped its humming. For an agonising moment Clara thought it had heard the chink of glass too. But the Orphan only leaned forwards to pick at the end of one of the tubes that was inserted into Hemlock's leg. No doubt it was dislodging congealed blood. Satisfied, it sat back, sucking its finger clean. The humming resumed, as did the little slaps of blood slowly filling the cauldron.

'Get ready,' Samuel whispered.

Clara heard the light swish of material, and a spell sphere appeared in midair. It arced across the room and smashed on the floor close to the Orphan. Green mist swirled and spiralled up to form a perfect duplicate of Samuel aiming his revolver at the wild demon's head.

The Orphan rolled backwards and jumped to its feet. The façade of an innocent boy vanished. White eyes with thick red veins glared at the figure of Samuel. Long black nails sprang from its fingertips, and its mouth was filled with sharp, glass-like teeth. It hissed and flicked out a long, blood-red tongue. Muscles bunching, it made to lunge forward, but the image of Samuel pulled the trigger. The power stone flashed, and the Orphan jumped back, raising its clawed hands to protect itself.

But the weapon and the man that fired it were merely illusions that disappeared after the shot, and no bullet had hit the demon.

A second spell sphere arced through the air and smashed at the back of the catacombs. This time a joint of meat appeared, skinless, still on the bone and wet with blood. The Orphan pounced on it hungrily. The instant it sank its teeth into the bloody meat, the joint exploded into a cloud of angry insects that swarmed over the demon and sent it writhing and screaming to the floor.

'Go!' Samuel shouted.

Clara ran for Hemlock. She willed her hands to stop shaking as she sawed through the rope where it was connected to the floor ring. The rope parted with a dull twang, and Hemlock fell to the ground in a bone jarring heap. He stirred and groaned as Clara yanked the tubes from his legs.

'You don't deserve saving, you bastard!' she hissed into his ear. 'But if you want to live, move!'

Hemlock became more alert then. He struggled weakly to get to his feet. Clara helped him and put his arm over her shoulders. He stank. They stumbled towards the archway, knocking the cauldron of blood over in the process.

The insect swarm had now dispelled, and the Orphan was back on its feet. Its red-streaked eyes widened at the upturned cauldron and the red meal going to waste on the floor. It then glared at Clara and Hemlock.

With sudden alarm, Clara realised the illusion spell had worn off. She was no longer invisible.

The Orphan screeched at her. The voice of reason in her head told Clara to drop Hemlock and run, but her body would not react. She was frozen to the spot. The Orphan stepped forward. Clara whimpered.

Then Samuel materialised, holding his revolver an inch from the demon's temple. And this was no illusion.

With a low and hollow spitting sound, the power stone released a burst of thaumaturgy. The Orphan slammed sideways to the floor. Its blood, black as night, bubbled into a pool around its head. There was a hissing sound, and the demon's body began to steam. Slowly it dissolved, as though made of ice and melting. The Orphan became a puddle of shadow, which was drawn into the ground until it disappeared completely.

Its grip on this realm severed, the demon had returned to the Retrospective.

Clara dropped Hemlock, and collapsed heavily on the floor beside him, breathing hard. Samuel gave her no respite. With a grunt he grabbed Hemlock and hauled him up onto his shoulder. Hemlock murmured and passed out again.

Samuel offered a hand to Clara. She grabbed it and allowed him to pull her to her feet.

The old bounty hunter clapped her shoulder. 'Let's get out of here before the police arrive.'