Sherlock Holmes lifted the edge of the net curtain to watch the girl oscillating on the pavement beneath. She was petite, with blonde hair twisted up in a neat chignon from which a single curl has escaped by her right ear. She was dressed fashionably but unremarkably in a black jacket, dark jeans and dark trainers and gave the appearance of someone who wanted to get lost in the crowd and remain anonymous.

Back and forth she went. A less scientific man would have imagine that all of those hesitating clients would wear a dip in the pavement outside his front step. As it was, he was well aware that it would take thousands of individuals centuries to do so. He was used to the dance of prospective clients. They would walk up to the step, raise their hand to ring the bell,and then when their finger was almost touching it, the hand would drop and they would walk away, only to double-back nine or ten feet down the street, hand raised again, finger closer to the bell each time until they got finally pressed it.

There was something different about this girl, though. She didn't have the poise of his normal clients. She was young, twenty four he estimated, possibly twenty five. She chewed the skin off the side of her fingers as she oscillated and it was that half forgotten habit that made him break with his tradition of non-engagement, push up the sash window and sticking his head out shout down, 'You could, come up you know. I don't bite - well at least, not often.'

She jumped at the sound of his voice, and looked up. 'I'm sorry, she said. I didn't mean to -'

'To what? To disturb me? You haven't. On the contrary, you might be about to make my day. Come on up.'

He walked over to press the unlock button on the entry buzzer and a few seconds later was rewarded by the sound of footsteps on the floor. Size four trainers, fifty-five kilos, no fifty-four he deduced as he went to open the door.

Three minutes later and the girl was installed on a chair. The chair. The client's chair. She was taller than he had initially thought, five foot three probably, but small framed with fine, even features and a button nose. Her dark blonde curls were pinned up in a messy chignon with a metal clip, but as he had noted previously, one curl kept escaping from the right hand side and she repeatedly pushed it back behind her ear in annoyance. John would find her attractive, Sherlock thought. His gauge for beauty. He found her not unpleasant to look at which was sufficient for him.

The girl had a quiet calm about her, despite her earlier jitters. Sherlock took up his own seat in the Eames chair, steepled his fingers and waited for her to begin to talk.

'I don't know where to begin,' she said, her eyes fixed on the skull on the fireplace as if seeking inspiration. Avoiding Sherlock's gaze or watching it for another reason.

Sherlock sniffed, catching an odd waft of a familiar scent. He closed his eyes to focus his senses, frowned, then got up, circled the girl, sniffing as he went. Trying not to invade her personal space. John has warned him about that.

'Is there something wrong?' she asked, looking puzzled rather than perturbed.

Sherlock's face broke into a grin as he worked it out. 'I presume you know Molly Hooper?' he said.

'Molly who?' the girl asked, turning round to look at him.

'Molly Hooper. I assume she works with you in the mortuary at Barts?'

'I don't work at Barts,' the girl said, as he circled round and resumed his seat. 'But how did you know about the mortuary?'

'Oh it's very simple really', he said, steeping his fingers again, speaking at rapid pace. You changed out of your scrubs but in your haste to get here you didn't shower. You still smell of the mortuary - sorry about that - it's an odd combination of disinfectant, embalming fluid and decaying human flesh that I'm sure you are familiar with. I presume you assisted with a post-mortem today, it's unlikely that your hair and skin would have absorbed that level of odour simply from working with refrigerated bodies in the mortuary. I suspect that at least one of the bodies that you worked on today was in an advanced state of decomposition. You left in a hurry, not so much of a hurry that you didn't take time to change out of your scrubs, but you were reluctant to remain in the mortuary long enough to shower. And you weren't looking where you were walking because you have a squashed maggot on the bottom of your shoe, presumably picked up as you walked out as I doubt those trainers are uniform compliant and nowhere near washable enough to perform messy post-mortems in.'

She stared at him, open mouthed for a good minute, then closed her mouth with a snap, narrowing her eyes suspiciously.

'How on earth did you know all of that?' she asked.

'I didn't know, I deduced it. It's what I do. So why don't you tell me what happened to bring you to my door at such a speed.'

'Do you mind if I get rid of the maggot first?' she asked, checking the bottom of one shoe and then the other. Pulling the offending object off with a tissue retrieved form her pocket, she asked, 'Can I put this in your bin? It's quite dead.'

'In the absence of a fish tank, that would seem very sensible,' he said. Indicating the kitchen with a tilt of his head his head.

She froze mid step, head whipping round. 'How the hell did you know about the fish tank?' She asked.

He sighed, 'Nearly every mortuary in the country has a fish tank in its relatives room,' he said with a dismissive wave of his hand. 'It is widely believed that the fish are relaxing. Besides they give the relatives something to focus on. Prevents those awkward silences. Decomposing bodies are common in mortuaries, and so unfortunately are the larvae from various flies. Mortuary technicians become fond of their fish and regard them as their pets. Owners enjoy treating their pets and what better to feed them with than a plump wriggling maggot or two, especially when they are present in such abundance after a post-mortem on a decomposing body?'

'APTs' the girl interjected.

'I'm sorry?'

'We're not called mortuary technicians, we're called APTs. Anatomical Pathology Technicians.'

'My apologies,' Sherlock said. 'So why don't you deposit your dead larvae unto the kitchen bin and tell me why you're here.'

'You mean you haven't deduced it yet?' she asked, after she had located the bin, placed the offending tissue in it, washed her hands at the kitchen sink with pomegranate scented fairy liquid (courtesy or Mrs Hudson) and returned to her seat.

'Enlighten me,' Sherlock said.

'Something happened,' she said.

'Well obviously.'

'Something - odd.'

'Define odd,' Sherlock said, starting to become interested.

'I was working in the fridge room,' she said. 'Checking tags at the end of the day. We do that - beginning of the shift and end of the shift, check that all of the bodies are tagged properly and that they're all present and correct on the list. Doesn't do to lose any of them or to have the labels fall off.'

'Heavens forfend,' Sherlock murmured, in a conscious parody of Mycroft. 'So what happened.'

'I heard someone talking,' the girl said. 'I thought someone was playing a trick on me. People do that. Especially to newbies. Hide on the racks and pretend to be corpses to make people jump, that sort of things. Everyone had gone home, you see. It was my turn to lock up.'

'But nobody was there?'

'No. I went outside and checked. I was the only one left in the department. But I could hear muttering. I even checked in the post-mortem room in case somebody had left a radio on, but there was nothing.

'So I went back into the fridge room and I could hear it - muttering. And then I listened closer and realized it wasn't muttering, it was praying.'

'Praying?'

'It was the Hail Mary, Mr Holmes. Somebody was saying the Hail Mary.'

He narrowed his eyes, considering. He was bored and wanted to be distracted, but nothing so far had grabbed him about this case. It was pivoting on a single question.

'In English or in Latin?'

'In Latin.'

And there it was, that spark that lit the flame, that jolted him out of his contemplation, that raised the case from a four to a seven. Maybe a seven and a half. That remained to be seen. Usually he wouldn't leave the flat for a seven but in absence of John, still absent on his honeymoon, a seven would do just fine.

He leant forward, hands resteepling 'And you're sure you were alone in the mortuary at the time?'

'Yes.'

'But you weren't, were you. In fact you were far from alone. You were in fact in a room with at least a dozen corpses in it.'

'Twenty seven ,' replied the girl automatically.

'Twenty seven?'

'We had twenty seven corpses in the fridge room today. One short of completely full. We thought we'd have to put up the pop-up racks but one got picked up by an undertaker.'

'So who were they?'

'Who were who?'

'The bodies in the mortuary.'

She shook her head 'I don't remember all of their names. I could probably tell you some of them.'

'No, not their names, that's irrelevant. I mean who were they. Were any of them Catholic? Was one of them a priest?'

'What - you believe it actually happened? You think a dead person could actually have been talking to me?' The girl's face made it clear that she had come here to be told that what she experienced was impossible. But if she really believed that, then why had she made the trip across London in such a hurry? So here then was a client who wanted to believe that they had imagined their experience, but for some reason knew that that they hadn't. The case had just hit a nine.

'What I believe is irrelevant,' Sherlock said with a sudden grin. 'What matters is that you believe it. Because if you didn't then you wouldn't be here. Come On!'

He stood up, grabbed his coat from behind the door, swung the door open and was halfway down the stairs before the girl had time to stand up from her chair.

To be continued...