Unprepared for the assault, she stumbled backwards until she felt the sharp edge of the top step beneath her feet. She seemed to hover a moment before falling into the yawning abyss.

She heard Robert cry out. She heard a sickening thud as her head struck the stone wall. She heard the rush of air roar in her ears as she made her spiralling descent and the curious crack her neck made just before she landed on the tower floor.

With blood filling her mouth and trickling down her face, she stared in stunned wonder at the shafts of silvery moonlight streaming in through the arrow slits.

And then, Deidre Monreith, daughter of Angus Monreith, bailiff to the great and mighty Lord Maxwell, heard no more.

Caerlaverock, Scotland, present day Caden Maxwell sat in shades of darkness listening to the harsh, hacking coughs of the dying man and couldn't help but marvel at the capriciousness of Fate.

He had once vowed never to lift a finger to find his father and now here he was keeping vigil at the emaciated man's bedside.

Four months ago, Caden had been in his loft in downtown Seattle, enjoying the fruits of his labour as a successful day trader in the futures market. He had a tight-knit group of college buddies he met every Friday at Bad Albert's Tap and Grill for burgers, beer and blues. He played football every Saturday morning at Brighton Playfield, met his mother for brunch on Sundays, and volunteered at his local Boys and Girls Club.

His hectic, fulfilling life left little time for thinking about his biological father and the hole his absence had once created.

Then he received a letter from a man claiming to be his father. In concise, contrite terms James Steward Maxwell had explained that he had recently been diagnosed with lung cancer, was not expected to live more than a few months, and wanted to spend his final days getting to know the son he had neglected.

Caden's first impulse had been to crumple the letter and toss it into the waste bin, but years spent at a Catholic school, being taught the virtues of compassion and mercy by strict nuns, had instilled in him a disproportionate dose of guilt.

Cancer. Dying. Regrets. Final days.

He wrestled with his conscience for a few hours and then he remembered the words his mother often told him when he struggled with an important, moral decision.

"Listen to the voice in your heart, Caden, and do what you feel is right."

Early the next morning, he dialed the number embossed on the bottom of the expensive, crested stationery, just beneath James Maxwell's scrawling signature.

After a brief, awkward conversation with James Maxwell, he clicked on expedia.com and booked the next flight from Seattle to Edinburgh.

One 3,000-dollar Air France ticket, a thirteen-hour flight with a brief layover in Paris, an exhilarating two-hour drive down the A702 from Edinburgh to Dumfries later and he found himself at Blackstone House, James Maxwell's ancestral home situated on six acres of parkland near Caerlaverock Castle and the banks of the Solway Firth.

James drew a long, wheezy breath that roused Caden from his musings. He sat up, leaned forwards, and studied the sleeping man, waiting for his chest to rise again. A moment later, James awoke from his narcotics-induced slumber, his eyes widening in terror, as violent coughs racked his body.

"I'll get the nurse, but try to relax," he said, in a calm voice.

Caden pushed to his feet and had barely made it a step when the door opened and the home health care nurse hurried in, syringe in hand. She jabbed the needle into the IV line connected to James' hand and pushed the plunger.

"This will help relax the muscles and make it easier for you to breathe, Mister Maxwell."

She checked her patient's pulse and then turned to Caden.

"I'll sit here all night, why don't you get some sleep?"

"Thanks, but I'll stay."

Caden put his feet up on a stool, crossed his arms over his chest, and settled in for a long, uncomfortable night. Hades, James's mangy looking but lovable Scottish deerhound trotted into the room, walked to the bed and rested his head near his master's withered hand, then flopped down on the floor beside Caden's chair, emitting a pitiful sigh in the process.

Caden's eyes were just beginning to close when he heard strange, warbling as if someone were singing somewhere far in the distance. He assumed it was coming from the small, stone chapel located a few hundred yards from the manor and closed his eyes.

The warbling altered to an otherworldly keening; a deep and throaty moan that sounded like a woman grieving.

Hades ears perked up. He lifted his head, glared at the window and growled.

Caden stood and walked over to the window with Hades scrambling to follow. Pulling back the drapes, he peered into the darkness but saw only his reflection looking back at him. Then he saw something, a red light, flickering between the trees.

Hades growled deeper in his throat.

The light faded and a woman in an emerald gown with long platinum blond hair floating around her shoulders stepped out of the woods. She seemed to stare at him and as she moved closer, the light of the moon illuminated her features. Her moaning altered again, switching to a high-pitched screech.

Hades suddenly stopped growling. Reluctantly, Caden looked away from the woman to the frightened dog. Hades began to shake and a puddle of urine spread across the floor.

"It's okay boy," Caden said, patting his head.

When he looked out the window again, the woman had vanished.

The next evening found Caden resuming his bedside vigil. Outside, the wind howled through the naked trees surrounding Blackstone House, causing them to bend and sway like skeletons performing a macabre dance. Even the trees seemed to be portending James's death.

He was about to close his eyes, when something outside the window caught his attention. A movement, a whitish smudge on the velvety ebony night. Jumping to his feet, he crossed the room and peered into the inky darkness, but saw only leaves skittering over the neatly clipped lawn and the dark woods beyond.

He dropped his forehead to the cool windowpane and sighed. What was wrong with him? Was he losing his mind? Had he imagined the mournful singing and the woman in the green gown?

Hades began to growl low in his throat. His ears pulled back.

"What is it, boy?"

But Caden knew.

Someone lurked outside James Maxwell's bedroom window. The beautiful woman with the face of an angel and the voice of a demon had returned. Caden wondered if she was one of James's jilted lovers or perhaps a long lost daughter?

The warbling began again.

With Hades on his heels, he raced out of the sickroom and down the stairs, nearly colliding with Mrs Harriet in the dimly lit foyer. The elderly housekeeper clutched a heavy flashlight in her wrinkled hands.

"Do ye hear 'at unholy wailin' the wind is making?" She placed the flashlight on the hall table and switched off one of the lamps. "It sounds like a bean shth."

Caden found it difficult to understand the woman's thick brogue but he thought she had said bean sheath.

What in hell is a bean sheath?

Before he could ask her what she had meant, Mrs Harriet shuffled out of the room, mumbling something about age turning her into a ridiculous daftie.

The warbling grew louder, stronger and Hades barked and lunged at the door. Caden looked out the window and saw the same red light he had noticed the night before, flickering in the woods beyond the front lawn.

He grabbed the flashlight before wrenching open the front door and plunging into the moonless night. It took a moment for his eyes to adjust but he could feel Hades by his side, hear his heavy panting.

The strange light suddenly disappeared and the woman in the green dress stepped out the woods, her long platinum hair floating about her shoulders.

Hades barked ferociously but the woman did not appear frightened. She stood between the skeletal trees and kept her gaze fixed on James Maxwell's bedroom window.

Hades took off running. The woman suddenly lifted her hand and the dog skidded to a stop. He spun in several circles, before stopping, bending his front leg, and pointing his nose in the direction of his master's window as if obeying some silent command.

Hades knows that woman.

Caden sprinted across the lawn. The closer he got to the woman, the more in-focus her features became. She had a beautiful face with almond-shaped eyes fringed by long lashes and pouty lips that reminded him of Angelina Jolie.

She looked at him then. Her eyes widened and she took a step back. Caden was almost to her when she took another step back and disappeared into the dark forest.

Caden clicked the flashlight on with his thumb and kept on running, weaving between trees and hurtling over logs. He could hear Hades barrelling through the underbrush behind him.

Finally, he saw her through the trees ahead of him.

She looked over her shoulder at him. Her mouth opened in a silent scream, her features changed from bewitching to hideous with wide, sunken black eyes, wrinkled skin that seemed to glow, and grizzled hair.

Caden suddenly felt feverish. His skin became slick with perspiration and his heart began to race. He had played competitive ball long enough to recognize the signs of a massive adrenaline dump.

I need to control my breathing!

He kept running but took slow, measured breaths.

Hades suddenly let out a terrifying yelp and forced Caden to abandon his pursuit.

He found the mangy beast only a few yards away, yelping and howling as if the hounds of hell were nipping at his heels. His collar had snagged on a lowlying branch and was choking him each time he moved. Caden quickly released the dog but by the time he had retraced his steps, the woman had vanished.

He considered abandoning the chase and returning to Blackstone House, but the adrenaline surging through his body propelled him on.

He walked through the woods, moving his flashlight in front of him in a wide, sweeping arc searching for signs of the woman.

Caden still believed the creature he pursued was merely a woman bent on revenge or mischief. A clever woman who was able to halt a charging deerhound with a single gesture, somehow alter her appearance, and slip over land littered with dry, crackly leaves without making a sound.

Doubt began to needle at him.

What if it wasn't a woman? What if it was one of the mythical creatures Mrs Harriet had prattled on about? If he had learned one thing since arriving at Blackstone House, it was that the Scots believed in the supernatural and revelled in telling stories about it. Ladies in white, headless horsemen, loch monsters, demons, fairies, phantoms. If he were to believe Mrs Harriet and the Guinness-fueled old men he'd spoken with at Gordon Pub, the hills and lochs were crawling with creatures.

His boots snapped twigs and crashed through the underbrush. The sound seemed amplified in the woods, making him feel unusually vulnerable. He didn't like feeling vulnerable.

The hairs rose on the back of his neck. Someone watched him.

He glanced over his shoulder, peering into the darkness. Only Hades followed, trotting several paces behind, his head hung low.

The sound of a twig snapping in the distance drew his attention. He swung his flashlight out before him, aiming it straight ahead. Nothing was there. The beam of light caught the spiralling descent of a brown leaf and Caden realized something was in the trees.

He raised the flashlight higher but nearly dropped it when he saw two glowing eyes staring back at him.

"Shit!"

Perched on a branch in a nearby tree sat a large grey owl, his obsidian gaze fixed on Caden. His head swivelled around, then he screeched, and Caden's heart stopped beating. The owl flapped his wings and flew off into the night sky.

Caden followed the owl's flight path until he came to the mudflats that led to the Solway Firth.

Hades growled.

Caden patted the dog's head, feeling the bristly fur on his palm.

"Be quiet, boy."

Although the wind had died down, Caden shivered. The long sleeved T-shirt he wore beneath his rugby sweatshirt was damp with perspiration and clung to his arms and chest.

The clouds drifted apart and silvery moonlight reflected off the placid water. That's when Caden saw her. The woman in green knelt at the water's edge and was repeatedly plunging a garment into the sea. Her hair, once again platinum blond, hung like a curtain around her face.

Caden clicked off the flashlight, motioned for Hades to stay, and then moved slowly, stealthily towards the water's edge until he stood close enough to see the leather belt knotted around the waist of her medieval costume.

Costume? Of course!

He realized then that she was probably one of the people who reenacted medieval life at Clash of the Centuries, the medieval fair held each year at Caerlaverock. Though he thought Mrs Harriet had said it took place in the summer, not late October.

She plunged the stained garment into the water again and then dropped her chin to her chest. The sound of her soft weeping floated on the sea-stained breeze.

Caden suddenly felt guilty for chasing and spying on a woman who had done nothing more than trespass and disturb the peace of Blackstone with her strange, mournful tune.

He reached out to touch her shoulder but his hand passed through her.

"What the?"

She looked up at him through her curtain of hair and gasped. Tears glittered like diamonds on her translucent cheeks. She was even more beautiful than he had first thought. He'd already noticed her kiss-worthy lips, but now he noticed her ample, round breasts which were almost disproportionately large on her petite, slender frame.

He tried to touch her shoulder again but his hand moved through her as if she were made of vapour.

She dashed the tears from her cheeks and stood, the top of her head coming to his chin.

"You can see me?"

"Yes."

"And hear me?"

"Obviously." Caden's thoughts spun around in his brain. He feebly grappled with the clues, trying to construct a logical explanation for the illogical situation before him. "Who are you? What are you?"

The ridiculousness of the situation struck him. He remembered the time he had been sick in bed with the flu and had channel surfed to an impossibly idiotic show called Ghost Hunters and how he'd snorted when the host had walked into an empty room of an old insane asylum and announced, "If there's anyone here, please make your presence known." Now here he was attempting to have a conversation with a transparent woman with banging curves and kissable lips.

"Five hundred years ago, I lived in a village near Caerlaverock. My name was Deidre Monreith."

Caden thought he detected a hysterical note in his chuckle. "Are you telling me you have travelled through time?"

She shook her head and the moonlight streamed off her hair like liquid silver.

"I am not a human from another time nor am I merely a ghost of what I once was. I am something far more tragic. I am a bean shth."

"I don't understand," Caden grudgingly confessed. "What is a bean sheath?"