For John, the hunt began after they killed Sarah.

During his waking hours he managed to steer his thoughts away from the tragedy, but in his Valium-induced dreams, it always came back, terrible and vivid.

They were leaving Cineworld on Renfrew Street in Glasgow after seeing the late-night showing of Chernobyl Diaries. Sarah didn't like scary or violent movies; she'd only agreed to go because John had insisted and she'd picked the last film. As they left the warmth and brilliance of the theatre building and headed for their car two streets away, she'd been slightly upset with John, saying that she was going to have nightmares for weeks now. Then she stopped in mid-stride, stared into the dark passageway to her left, and screamed.

John saw the two men a second later. At first he thought they were homeless people about to accost them for money. But when they stepped into the dirty light of the street lamp, he realized that while they may have been homeless, they were NOT people.

People didn't gleam like phosphorus in the dark or have pupils so huge that their eyes were beady and black, like those of rats or crows. Nor did they have jaws packed with abnormally long teeth that brought to mind a shark's mouth. And unless they were psychotic or on powerful hallucinogens, they didn't swoop upon a screaming woman, tear her throat out, and feast on the rich red blood, ensuring that Sarah would never have nightmares about the movie after all.

John emerged unscathed only because a midnight bus turned onto the deserted street at that moment, having been detoured because of a car accident on Killermont Street. Its headlights illuminated the carnage, sending the photosensitive creatures back into the alleyway. Their hellish growls and hisses were the last thing John heard before he fainted.

The authorities attributed Sarah's death to drug-precipitated violence. The press followed suit, pointing to recent examples of people committing gruesome acts while under the influence of LSD, PCP, or mescaline. John didn't dare contradict these published statements with the truth. First, no one would believe him, and doubts about his mental fitness could have resulted in the loss of his medical license and even his freedom. Second, he didn't want the hunters to know that they would now be the hunted.

"You're sure this is the place?" Mike Stamford asked yet again.

"That's what the e-mail said," John whispered as he swept the room with torchlight. "Remember, this Sherlock –whoever the hell he is- has never been wrong yet."

Stamford nodded reluctantly and wiped the sweat off his round face. "Let's do one more sweep. If we can't find any uglies, we should leave. Maybe they moved on, or Sherlock is wrong for once."

John didn't think so. There was a faint copper tang in the air that he recognized all too well, both as a doctor and a vampire hunter. But to humour his friend, he said, "Fine."

The two men held their machetes close as they re-explored the boarded-up shell that had once been a convenience store. Beams of light from their torches scanned the graffiti-littered walls and illuminated the dark spaces behind the rusted refrigerator and ice machine. A fire started by a careless meth cooker had gutted the interior, leaving man-sized piles of burnt wood and melted plastic for them to dodge around.

John had killed his first vampires –a man and a woman- in a similar place. Once he'd accepted that they existed, finding them had been easy. They hovered outside nightclubs, late-night movie houses, 24-hour cafes, and other places that attracted their human prey after darkness fell. Contrary to what some films and novels preached, they were not gorgeous immortals who approached unwary night owls, promising sex but delivering death instead. They were grotesque urban sharks who ambushed and devoured stragglers before slinking off to filthy rookeries to hide from the daylight.

On his first hunt, John spotted two of them lurking in the alley next to an all-night diner, and followed them back to their lair –a vacated video game parlour. When the sun rose, he infiltrated the place and quickly killed the male vampire with a vicious axe chop. The woman tackled him while he was distracted, and would have ripped his throat out had he not stumbled against the boarded-up window frame and fallen through it, dragging her with him into the daylight. In seconds, she was a pile of cinders- much to the delight of some tripping junkies lying on the pavement nearby.

As a former soldier, John wasn't afraid when he hunted. But he wasn't reckless either. He studied his enemy, online and in archival texts at the library, and soon learned what could kill them (sunlight, decapitation) what would slow them down long enough for him to escape (bullets), and what just pissed them off (garlic, crucifixes, hero worship). As he prepared for battle each night, John often wondered if there were others like him: people who'd lost loved ones to vampires and wreaked vengeance until they were either injured, or killed, or something.

The high mortality risk that went with his new obsession didn't scare him any more than the hunt itself. His military service had been a prep course on how to die for your country. John was certainly ready to die for mankind if he had to.

It was after his tenth kill that he began to get e-mails from a mysterious Londoner who called himself Sherlock Holmes. John had no idea how Holmes found out what he was doing, but the information the man supplied was welcome. The messages, which were sent to John's private account, contained addresses for vampire nests all over Glasgow. When John checked them out with Mike Stamford (who became a fervent believer after John saved him from a newly created vampire in the hospital morgue), he invariably found them occupied. He always asked 'Sherlock' how he came by this information, but never got an answer.

Intrigued, John researched Sherlock Holmes online but only found an obituary for a man who'd died two years previously, aged thirty-four. Cause of death was listed as accidental. The deceased was a well-known freelance detective who'd left behind a brother, Mycroft. John was tempted to contact the surviving Holmes somehow and let him know that someone was using his dead brother's name, but decided against it. His still-raw feelings over Sarah's death left him reluctant to resurrect another's pain.

"John? Did you hear that?"

Stamford's voice jerked him back to the present. "Hear what?"

"Listen!"

John obeyed. At first he didn't hear anything. Then footsteps sounded in the dark hallway that led to the shop's delivery entrance. He tensed as they grew louder. There were two of them, one considerably heavier than the other.

He raised his machete, but something wasn't right. Vampires, unless they were in daylight hibernation mode (it was now eight in the morning) would have heard and smelled the two men as soon as they broke into the building, and there would have been a fight by now. At this time of day there was no way that an undead straggler would be coming home.

A couple of street kids, maybe?

Two lights appeared at the end of the hall, and grew bigger and brighter until a man and a woman appeared in the doorway. John and Mike exhaled at the same time and lowered their weapons, because the newcomers –with their clear eyes and healthy colouring- were clearly human.

The man was in his late forties, with silvery grey hair and a serious expression. He carried himself like a policeman or soldier. The woman was no older than thirty and wore her long brown hair parted on the side. She chewed her lower lip in what John perceived as an anxious gesture. Both of them held a torch in one hand and a thick-handled ax in the other. Even in this area of Glasgow, they must have drawn stares when they entered the building with such weaponry.

"John Watson?" the man asked.

Mike shot a startled glance at his friend. John frowned. "Who's asking?"

"I'm Greg Lestrade." He indicated the young woman with a nod. "And this is Dr. Molly Hooper. We arrived in Glasgow from London last night. To find you."

"Find me? Why?"

When Molly answered, John and Mike received their second surprise of the day.

"Sherlock Holmes sent us. You need to come to London right away."