Disclaimer: I own nothing but the storyline

This is my first fic that I've been brave enough to submit so reviews would be greatly appreciated :D

Dr. John Watson was sitting at his laptop after completing his most recent blog. He sighed; Sherlock was still not enamored with the idea. His scathing criticism and sarcastic jibes were inevitable. He rubbed the back of his hand over his tired eyes before walking away from his laptop into the cluttered kitchen. He shook his heads at his flat mates latest experiments before putting the kettle on to make tea. He heard the front door open and light footsteps begin to climb the stairs.

'John! John, where are you?' Sherlock cried as he burst through the door to the kitchen. His eyes fell on John, 'Get your coat,' he demanded.

'Why, what's happened now?'

'I'll explain in the cab, it's waiting downstairs. Lestrade text me this morning, I've already had a look at the crime scene. Get your coat John, come on!' Sherlock shouted as he turned and walked out to the cab.

John stood still for a moment thinking. He briefly contemplated refusing to follow and letting Sherlock go on alone but his need for excitement and danger was overpowering. Sighing dramatically, overplaying the disgruntled flat mate for effect he grabbed his coat and followed his tall curly haired companion down the stairs into the cab.

'What's happened then? What weird and wonderful crime has been committed that Lestrade needs your help?'

'Double homicide,' Sherlock answered dryly, looking away from John out of the cab window.

'Was it brutal?'

'Homicide is always harsh John but this killing was not a violent one.'

'Then why does Lestrade need you then?'

'He's out of his depth as usual.'

'But why, what's so special about this case?'

'You'll see when we get there why I'm needed,' Sherlock replied elusively.

John contented himself with watching London go by, he knew he would get no further explanation from his surly companion. He glanced across the cab at Sherlock, his face was fixed in a scowl and his hands were clasped in front of him. However many of these awkward, silent cab rides he took with Sherlock he swore he would never get used to them, each was as weird and thrilling as the first.

They arrived at an end terrace house in East London, the road in front and to the side cornered off with police tape. The front garden was crawling with officers and forensic experts. They were quickly led through the assembled officers by a snarling Sergeant Sally Donovan. She pointed into the master bedroom with a look of pure disgust in her face.

'Freak she spat at Sherlock's retreating back. A whimsical smile crossed his face before he partially turned his head towards her, his face once more serious, and asked her, 'How is Anderson's wife?'

John repressed a smile as Donovan's face fell. 'You…I…No…How?' she stuttered. Sherlock turned to give Donovan an evil smirk before motioning for John to follow him into the room.

John walked into the bedroom and surveyed his surroundings. A young couple lay in the double bed as if they were sleeping peacefully. On closer inspection the couples' complete motionless confirmed that they were both dead. He turned to look at Sherlock, a look of pure confusion on his face.

'Well, you're the doctor, tell me how they died.'

John walked closer to the bed checking both bodies for pulses, blood and bruising.

'No blood, no bruising around the neck but they appear to have died from oxygen deprivation,' John thought out loud.

'No DNA, no fingerprints and no signs of entry. There was no struggle, they never woke up,' Lestrade added.

'No leads at all?' John asked incredulously as he stood back from the bed.

'None,' Sherlock interjected, "That's why they need me.'

'So, how do you think they were killed then, Freak?' Donovan bitterly hissed from the doorway.

'They were suffocated obviously.'

'Ha! If nobody but them entered this bedroom how were they suffocated?' Donovan laughed.

'In the usual way, they were deprived of oxygen and therefore died in their sleep.'

'They weren't chocked, they weren't smothered so how were they killed Sherlock?' Lestrade shouted, his patience snapping.

'It's obvious, isn't it!' Holmes cried. 'Somebody has made this room airtight, unknown to the homeowners evidently.'

Watson, Lestrade and Donovan stood bewildered, staring at Sherlock open mouthed.

He growled in the back of his throat before shouting at them, 'How can you not see it? I am astounded by all your ignorance.'

He stalked over to the bedroom door and closed it in Anderson's face as he was about to walk into the room. There were very muffled shouts from the hall that Sherlock completely ignored.

'Look at the door, what do you see? What is different about this door to every other door in the house?'

'Why don't you stop wasting our time and tell us!' Donovan snarled.

'Listen to the door as it closes,' Sherlock commanded before opening the door and closing it again dramatically.

' I didn't hear anything,' Lestrade sighed and the other two shook their heads.

'Come closer and listen to it open then.'

The three confused spectators shuffled forwards and craned their necks to hear what Sherlock was going on about.

'It sounds like a fridge opening!' John exclaimed.

'Exactly!' Sherlock cried. 'Somebody has installed a vacuum seal on this door like, as John said, you would find on a fridge. This stops air entering the room from the rest of the house.'

'So somebody must have installed it yesterday as these two died last night,' Donovan announced triumphantly.

'Wrong,' Sherlock cut in. 'Firstly, does it look like any work has been carried out in the hall in the last few days, it is far too clean. Secondly, when I took a look at the crime scene this morning I examined the outside of the window. Around the window frame there were remnants of a waterproof, airtight putty which is usually used to waterproof welds and plumbing. Somebody smeared this around the window, risking being seen by neighbours or the houses behind. They were getting desperate, the door was not working on its own, enough air was entering the bedroom for the couple to survive the night.'

'How did they know that the window was the source of the oxygen and they did not sleep with their bedroom door open?' Donovan quipped, trying to find a flaw in Sherlock's logic.

'The killer must have had access to the couple and their bedroom. He is clever, devising this plan to kill this couple. He wouldn't have risked discovery or wasted time installing the seal on the door if they knew it was going to be open all night. As for knowing the seal of the window was not air tight, take a look at the wall paper surrounding it. It shows obvious signs of damp where the rain has leaked in. The killer must have seen this or been told about it to know to place the putty on the window frame.'

'OK, so how could he be sure that the couple would have their window closed? Sleeping with the door closed is a habit but it was warm last night, they may have had it open' John asked.

'John is right Sherlock. I've talked to the neighbours and they say that the couple usually slept with the window open and when they went to bed at nine thirty the window was closed,' Lestrade interjected.

'Last night in London two inches of rain fell between ten pm and two am accompanied by strong winds from the North. This bedroom is North facing so the rain would have been blown in if the window was open further exasperating the damp. Either through their own common sense or acting on advice they closed the window last night.'

'So your saying the killer went out in the rain and the wind, climbed up to the window and applied the putty after the window had been closed,' Donovan snorted.

'Yes and I can prove that somebody entered the garden last night after it began to rain.' Sherlock said smugly before rushing down the stairs. Lestrade, John and Donovan followed him down the stairs with the still grumbling Anderson close behind them. When they went out of the house Sherlock was standing by the side gate, bending over a patch of mud where the grass had been worn away by frequent use.

'Two sets of footprints in the mud. So there were two of them?' John asked.

'No. Anderson stepped in the mud when he entered the back garden to look for DNA evidence, I heard him complaining about his shoes,' Sherlock muttered darkly. 'The larger prints are Anderson's the other set, about a UK size nine I'd say, belong to the killer.'

'How can they be sure that they are the killer's prints, by the look of it lots of people use this gate?' Lestrade asked pinching the bridge of his nose.

'Last night was the first time in over a month it rained in London so the prints must be fresh. None of the neighbours entered the garden before the police were alerted, they were found by the deceased female's mother who was picking her up for a hospital appointment. The only officer on site with muddy shoes is Anderson so therefore the most probable owner of the prints is the killer.'

Sherlock nodded towards Lestrade before walking away, 'Text me if there are any further developments ,' he called over his shoulder.

John offered a small smile to Lestrade and Donovan before running to catch up with Sherlock; 'Any idea why she was going to the hospital this morning?' John asked.

'She was pregnant.'

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