John stepped across the frozen tarmac and stared at the thing ahead of him. The tower was exactly the same as it had been in the picture, except the vines snaked over the window now, and the glass was coated with a fine layer of dirt, cracked in the middle by a stone. It looked less like a castle tower up close, and more like a monster with teeth and claws and burning eyes that could see into your soul. It was a villain's lair, an ogre's keep. John eyed it for a second, forcing himself to stay calm. It was just a building. He had been in thousands of buildings.

A stiff wind caught John's cheek and pulling the jacket closer to his chest, he walked forward, his eyes narrowed against the cold. The door loomed in front of him, the mouth of the beast. John tapped the door handle and to his surprise, it swung open. Someone had been expecting him.

The thought bounced into head before he could stop it, and he had to bite down a tortured scream. He had seen so many things in his life - so many deaths and tragedies and crumpled bodies - but nothing could stop the terror rising up inside him. What if this whole thing was a trap? What if he was going to be killed? What if this? What if that?

John stepped forward into the dark tower and tried to control his breathing. This was a walk in the park compared to what he had done in Afghanistan. Why should he be worried? Another step and another and another, until he was standing at the wall. His hands searched it for a light switch. No luck. Cursing, he raked around his pockets. It was in here somewhere...there. His hand curved around a tiny key ring and he pulled it out, flicking the button as he did so. A thin beam of light shot out, illuminating the dust that danced in the air. It wasn't much, but it was better than nothing. Swivelling the light, he found the stairs and began to climb.

The light from the open door downstairs vanished as John walked and his heart beat faster, a bird fluttering against the bars of its cage. There was nowhere to run should someone jump out at him - a wall on one side and a dizzying drop on the other. Twice John had glanced down and seen a dead rat, its tail curled into its back and its teeth covered in dried blood. John thought of the fox in the picture and how sly he looked, how he seemed to be winking at the camera. A shudder raced up John's spine and with a gulp, he tightened his grip on the torch.

After an eternity, the beam of light from the key ring hit against something solid. A door. John walked towards it, his hand outstretched and his heart battering against his rib-cage. This was it. The moment of truth. Was he wrong? Or, even worse - was he right?

The door, just like the one downstairs, opened effortlessly, and John gingerly stepped into the room, wishing he had brought his gun. Pale sunlight streamed through the window, hitting the dusty floor at odd angles, reflecting off broken glass. John looked closer - it wasn't glass. It was a mirror.

John took another step into the room, an old leaf crinkling under his foot.

He swallowed a boulder and turned his head to the side.

No.

A girl with long blonde hair was propped up in a chair, draped in shadows. The sunlight didn't touch her, but John could still see her skin, paper thin and cracked, in the light of the torch. Her cheeks caved in and her nails were daggers, sharp and pointed. She was wearing a pink dress and a purple cardigan, but they drowned her, the swathes of fabric hanging off her limp frame. Her arms were twigs; her legs were sticks.

You didn't have to be a doctor to see she was dead.

You didn't have to be a detective to see she had been starved.

John turned away and vomited into the corner, bile sluicing over the concrete floor. His hands were shaking and his breath came in ragged gasps. He didn't know what he had been expecting - puppies? A box of cupcakes? - but just that single glance, that single image made him want to throw himself off the tower, onto the cold hard concrete below.

With trembling fingers, he wiped some vomit from his mouth and pulled his phone from his pocket. He pressed the buttons for the flat and waited for Sherlock's voice. Nothing. Just the endless beeping and finally, the automated voice of the answering machine. John swore and pushed his phone back into his pocket. He didn't have Lestrade's number, and there was no way he trusting the whole of Scotland Yard with this. No way.

John turned around and immediately stumbled backwards, his breath caught in his throat and his hands stinging from the fall. A long figure, tall and lonesome, stood in the doorway. There was something familiar about it. Something recognizable. John searched for a threat, or a warning, but only managed a strangled, "Shit."

"I thought you would have been pleased to see me, John." Sherlock's willowy frame emerged from the doorframe and John struggled to his feet.

"For God's sake, Sherlock, can you sneak up on me like that?"

"I didn't sneak up on you - I've been watching you for at least five minutes." Tilting his head, Sherlock regarded the skeleton in the corner. "Another victim."

"Yes, yes - how did you know I was here? Did you follow me here, or did you just use you bloody physic powers?" John swayed on his feet, still feeling lightheaded and queasy.

"Haha, hilarious, John. Firstly, I didn't know you were here. The killer is either intimately aware of my lack of knowledge, or he simply wanted to make sure I didn't miss the clue. There was another one, John, another clue. At first I didn't see it, but then, I did - sewn into a patch on the dress, the words Bad Wolf."

"You stole part of the dress? How did you even-"

"It doesn't matter. I came here as quickly as I could. And secondly; Internet history, John. You should really learn to delete it."

John opened his mouth to speak and then promptly shut it. What was the point? Sherlock's brain was so fast, so cutting, arguing with anything he said was practically a death wish. John gritted his teeth and wandered over to Sherlock, who was now investigating an interesting piece of floor. "Should we call Lestrade?"

"Yes, we will. No now. Can't have him destroying a crime scene. Nothing better than first-hand evidence, and I can't have him and his...cronies messing it up."

"Sherlock..."

With a sigh, Sherlock dug into his pocket and threw a phone at John. "Fine, call him. But be quick about it. We have work to do." He gave John a quick glance and then went back to examining the floor, his long fingers stroking the grey ground.

John watched him for a moment and, still feeling slightly sick, searched for Lestrade's number. It wasn't hard - Sherlock only had about four contacts. John. Mycroft. Lestrade. Mrs Hudson. Touching Lestrade's name, John waited for a voice.

"Hello, this is Greg Lestrade."

"Yes, hi, it's John. Watson. I'm at the Bad Wolf Tower, Tyler Road and well...you'd better come down and see for yourself."