The Doctor opened the door of the TARDIS,expecting to see a white sunny beach with swarms of people. Instead, what he saw was a deserted alleyway in what looked like 19th century Britain.

"This isn't the Great Seashore of Zvahaltana" he said disappointedly (after his recent escapade with Toclafanes and Time Lords and then nearly crashing the Titanic into Buckingham Palace, he had been looking for somewhere nice and sunny).He hopped out of the blue box and walked down the alley. It was a typical cobbled path with small houses and shops along it-nothing out of the ordinary. Except, of course, for the fact that there were no people in sight. "Now that's odd .Where is everybody? And why," he said, squinting his eyes into the misty path ahead "is it so foggy?" His curiosity aroused, he walked faster, and saw straight ahead of him a young boy running off to the left.
"Oi!" He cried, running after him. The boy stopped in his tracks and looked around. "Hello", said the Doctor, giving him one of his charming grins. "Hello" replied the boy, staring at the Doctor with his eyes narrowed, as if he were analysing him. Apparently unable to deduce anything, he asked "Who are you?"
"I'm the Doctor."
"Doctor who?"
"Nothing. Just the Doctor"
"But what kind of Doctor? A medical one? Or a scientist or an academic of some sort?"

The Doctor grinned widely and said "Everything" with a twinkle in his eyes.
The boy began to speak, and managed a confused "but" before the Doctor cut him off
"That's enough questions from you-now it's my turn! Where were you running off to?"
"Home. I'm late-I was supposed to be there by 5."
"Hmm. and where is home?"
"Oh it's just a bit further from here"
"Yes, but where is here? Where am I?"
The boy gave him a wary look.
"Are you drunk, sir?"
"Nah-I was just bopped over the head. Woke up unconscious-couldn't remember a thing!" He replied, sounding as though being a bopped over the head was a delightful thing that happened to him every day.
"So," he pressed on, "Where am I?"
"You're in Edinburgh, sir"
"Oh no, enough with the "sir"! Just-The Doctor."
"Okay, Doctor"

"Brilliant. And what can I call you?
"Arthur"
"and how old are you, Arthur?"
"12"
"Right. Also, can you tell me what year it is?" he said, adding "I was was hit very hard" as an afterthought.
"Right, well, It's 1873"
"Hmmm. Interesting. Right then, Arthur-you were going home weren"t you? Let's go then!" said the Doctor, beginning to walk ahead
"Hang on a minute!" protested Arthur "I can't just take you home like that! I don't even know who you are!"
"Oh right,sorry,my mistake" said the Doctor, fumbling around his coat pockets till he finally pulled out a small rectangular piece of paper and held it up for Arthur to see. "I'm an investigator from the Society of..Investigating...Stuff." he said, and quickly stuffed the paper back into his pocket.
Arthur's face lit up at the word "investigate". "Really? Fascinating! What are you investigating?"
"Stuff. What sort of stuff has been going around here? Something very strange I assume, going by the fact that the streets are so...isolated."
"You're quite right-very strange stuff indeed! All those people disappearing-the whole town's scared! That's why no one's out at this time. This is when the fog comes"
"Fog? What fog?"
"This fog. The mist-makes it harder for people to see, doesn't it? Harder to see, and easier to get abducted"
"Right…These people that disappear-have any of them been found?"
"No, si-umm, of the earliest...well...they were found dead.
The Doctor merely nodded, his face looking into the distance, frowning with , he snapped out of it and smiled at Arthur.
"Well then-we wouldn't want you to be caught, would we? Let's go home then!"

"Doctor Who?"
"Nothing! Just-The Doctor!" explained the Doctor exasperatedly to Arthur's mother.
"Don't worry, mother, he's an investigator!"
"Oh off you go again with your investigation nonsense! With your deductions and analyses and what not" muttered his mother.
"No-Arthur's right ma'am, I am an investigator" said the Doctor, flashing the psychic paper at her.
"OH! "She exclaimed, "You're here to investigate those horrible disappearances and deaths, aren't you?" The Doctor nodded and strode into the house.
"Well then, we'll do anything we can to help!"
"Good! I'd like to ask you some questions. Number one-How many people have been taken? Number two-does the mist come every day at the same time? And number three-what about the dogs?"
While his mother looked confused, unable to give a proper response too so many questions simultaneously, Arthur responded clearly.
"Around seven people have been taken till now. Three of them are dead. The mist comes every day at the same time and I'm sorry what did you say about the dogs?"
"Dogs. While coming here I saw a few dogs walking about the streets"
"Well of course-they're strays"
"So nothing's been happening to the dogs then?"
Arthur looked quite puzzled. "No...I don't think so...what does it matter? They're dogs."
The Doctor had that distant look on his face again-like he was somewhere else, running through stores of information, or doing a thousand calculations, all at once in his head.
"Right, of course, it doesn't matter" he said, still maintaining that look. "All these people that are found dead-what do they die of?"
"We don't know" said Arthur's mother. "The police inspected them and they said that they haven't got a cause of death quite yet."
"Yes, but..." started Arthur, glancing uncertainly at his mother
"But what?" Asked the Doctor sharply.
"Well. It's just that people are saying that the police are hiding something. They say that the people that were found were…Torn apart…They had been ripped to pieces…as if mauled by some vicious beast...and their bodies were slashed and.."
"Rubbish." said Arthur's mother firmly, cutting him off mid-sentence. "That is all rubbish. Nothing but rumours spread by mischief-makers to cause panic"
"well, there's always some truth behind rumours."
"Be as that may" she said sternly "There's no reason to go spreading it around town, creating fear I peoples" minds. We ought to just let the police do their work peacefully. They'll catch the criminals within no time."
"Yeah I'm sure they will" the Doctor muttered under his breath.
"Well then," he said, suddenly jumping out of his seat "I'll be off!" He headed towards the door, but Arthur ran across the room and blocked his way.
"You can't go outside!" he exclaimed.
"Sure I can have to go outside and investigate!"
"Well then I want to come too!"
"You can't! It"s too dangerous!"
"Well how come it's all right for you?"
"Well I'm a professional. From the Society of Investigating Stuff"
He walked around Arthur and put his hand on the doorknob. Just before turning it, he turned around and looked at Arthur's mother
"Make sure he doesn't come out." he said.
She nodded, and said "But what if you get caught?"
His eyes twinkled in that mysterious way again. He grinned widely and said "Oh I'm counting on it" before shutting the door behind him.

"I thought I told you not to follow me!" The Doctor exasperatedly told Arthur.
He had been walking through the streets, just generally observing things, when he saw Arthur peeking at him from behind a wall.
"Yes, but I want to investigate too! Please let me come with you?"
The Doctor looked like he was about to argue, but then he changed his mind. "Oh all right," he said "but you have to be careful! Don"t go wandering off or anything!"
"Yes I promise I won't!"
" ," said the Doctor, walking into the deserted Town Square
"Where were we? Ah-the fog."
"What about it?"
"Well...it's just very odd, it's not regular fog...it feels funny"
"the fog feels funny?"
"Yes. And it's not equally distributed" he said, pulling out his sonic screwdriver and scanning the area around him. Arthur's eyes widened at the sight of the sonic device. "What is that?" he asked, his face lighting up with wonder.
"It's a screwdriver." The Doctor replied, putting down the screwdriver with a slightly confused look on his face
"That's odd"
"what is?"
"The fog. The mist. Its concentration levels are higher in some areas than others. Which brings me to the dogs."
"Why do you keep asking about the dogs?" asked Arthur, nonplussed
"Because nothing seems to be happening to them."
"Well obviously! Who would want to kidnap a stray mongrel?"
"No, I'm not talking about the kidnappings! I'm talking about the fog. The dogs aren't affected by it, but all the humans are scared of it-it makes it difficult for them to see. Take a look at you-you've been bumbling around and tripping and falling because of it. But the dogs are moving around perfectly all right-their eyesight is fine. Now why is that?"
"I don't know" replied Arthur, baffled.
"Let's go find out then! Right-first of all, we need to find a dog."

He started walking ahead with Arthur beside him, both of them clicking their fingers and whistling and Arthur shouting "Here doggie!" in the hopes of finding a dog. They continued moving this way, till the finally found a large canine at the end of an alley. Arthur clapped his hands and whistled, beckoning the dog towards them. The Doctor stood still, staring at the dog with that same look of concentration. The dog sat there unmoving, oblivious to Arthur's calls, its gaze fixed on the Doctor.
"What's different about you?" muttered the Doctor under his breath
"Oh…oh! OH!" he exclaimed, each "oh" getting progressively louder as sudden realisation dawned on him.
"Hmm yes-I see!" he continued, his enlightenment spurring him into action as he paced, and ran his fingers through his hair agitatedly "The collar-a filter-of course! But how..." He took a step towards the dog, when it suddenly opened its mouth widely.
"Arthur! Step back! "Cried the Doctor, hurriedly retracing his steps. A green gas coming out of the hound's mouth was the last thing he saw before the darkness enveloped him as he and Arthur fell unconscious.