John approached the steps up to 221B's front door with dread.

This was not right. This was his home.

But still, he was not relishing the idea of coming back and finding Sherlock once more deep in conversation with the service provider woman. She had never introduced herself, and Sherlock had said only, "Why does she need a name?"

"Because she's a person," John said. "With feelings."

"I don't pay her to have feelings," Sherlock said callously, and continued to read Le Monde.

"You keep saying you don't pay her at all," John pointed out.

"Nevertheless. It is a business arrangement and I am the client." He flicked the paper dismissively.

"One of her favourites, I bet. The one who doesn't even acknowledge her name."

Sherlock had glanced at him with amusement. "Are you jealous, John?" He did not specify, of whom.

"Don't be stupid. It's just a courtesy thing."

And then Sherlock had lowered the paper to look at him with that contemplative dark gaze, and John had given up and gone out.

Now, John hesitated. Would Sherlock be with... whatever her name was...or worse, would the flat be empty?

Twice this week already Sherlock had arrived home at dawn, hair damp and unruly, the back of his Belstaff coat soaked. He offered no explanation and John didn't ask.

Sherlock did say the first time, "Have you sat there all night?" upon finding John upright on the living room sofa, a blanket draped over his striped jumper, reading an old case file.

"Yes," John said.

"Not necessary," said Sherlock, and went into his room and shut the door.

And that was it.

Not tonight, John thought. No way was he going to sit at home like some desperate loser, waiting for Sherlock to get home safely. There had been no signs that Sherlock was in danger - either from drugs, or this woman. Quite the reverse. He seemed cheerful, playful, hugely engaged.

It was John who sat alone and isolated.

Of course, it might not be the woman who was occupying Sherlock's time. It might be a case that Sherlock was working on without John.

Actually, that idea hurt more.

John spun round at the top of the steps, and jogged back down onto the street. He was young - youngish - free and single. There was company and comfort to be found in this city, even if none of it was at home.

He did not glance up to see if Sherlock was watching from the window.

"John - John Watson?"

His name, called uncertainly across the heads of the crowd in his usual pub in Camden, a big place which frequently had live music and always had a noisy clientele.

John looked around fuzzily, head full of beer and bitter reflections.

The blonde woman, that no name service provider woman, was standing next to him at the bar.

She gave him a radiant smile.

John looked around for Sherlock.

"He's not here," she said. "Said he was going out. Working on something."

"Right." John nodded neutrally. The last thing he felt like right now was a chat with this woman.

"Can I get you a drink?" she asked, reaching for her purse. She was dressed far less formally tonight, in a soft large-check shirt, black fitted jeans and black strappy sandals. The creamy skin and beautiful eyes were still in evidence, though, and as she stood beside him John became aware of her perfume, a light citrus scent which wafted from her...cleavage.

He moved his gaze firmly to her face. "I don't even know your name. Your real name," he added.

"Theresa," she said, and held out her hand to shake his.

There was nothing of the businesslike about her here, in this glazed-tile pub, surrounded by happy punters waiting to hear the band.

John shook her hand. "John," he said. "But you know that already. You probably know all about me."

"Only what Sherlock has said, and that, I'm afraid, I can't repeat. What are you having?"

Drinks in hand, John led her through the crowd to the terrace round the back, and they perched on a picnic bench close to the patio heaters.

They clinked glasses and sipped. John could think of no opening gambits, and kept getting tantalising drifts of lemony scent.

Theresa smiled at him. "I'm glad I spotted you. I was meant to meet a friend here, but she's not going to make it. Are you here on your own?"

"Yeah."

"The band are ok. I saw them a couple of months back."

"Right. Great."

She reached out and touched his hand where it held his pint. "I'm sorry," she said.

"What's that?"

"I said, I'm sorry. You must feel like I've barged in on your life with Sherlock and stuck my oar right into your friendship."

She was gazing at him calmly but with a slight sadness which only made her eyes more startling. John had never seen eyes so blue. No. They were grey. -It depended on the light.

He let his shoulders drop. "A bit," he admitted. "I haven't seen much of Sherlock since he started seeing you."

She laughed. "You do know my relationship with him is purely professional, don't you?"

"I don't know anything," John told her, "and this whole business was my idea."

Theresa sighed lightly. "So that's why he's doing it." She caught herself. "Sorry. Doctor patient confidentiality."

"You're a doctor?" John gawped at her.

She smiled. "A service was identified. I am the provider."

John sipped his drink and pondered this for a while. That piece of news had an unpleasant whiff of Mycroft about it.

He decided to ignore it. "So, is Sherlock OK? As one doctor to another."

"What do you think?"

John grimaced. "He's impossible to read unless he wants to be read."

"That's my experience, yes. Why did you ask if he was ok? "

"Just..." John felt like a louse for even mentioning such a personal thing, but still: "He's become obsessed with learning about love. He thinks it's going to bring him benefits, give him some kind of advantage if he has experienced it."

In for a penny, in for a pound. John took a breath, then said, "That's what made me suggest seeing a - professional."

"I see."

Her eyes were twinkling. "No wonder you've been so uncomfortable around me."

"Does Sherlock know you're a doctor?"

"I'm sure he would if he thought about it, yes, but he has designated me only as his empty vessel to fill, to help him... to help him."

John knew a little about this area of psychology. "To help him feel less empty."

"Yes."

The idea that Sherlock felt empty tore at John's heart.

"That upsets you," Theresa said. "I think you feel empty sometimes too. That's why it works so well, your friendship." Her hand was still resting over his, John noticed.

"Thank you for not assuming we're sleeping together."

"Let me tell you something," she said. I" didn't have an appointment with Sherlock tonight. But when I heard from him that you weren't back yet, I came here hoping to run into you."

"Me?"

She let her fingers move across the back of his hand, and he did not protest. "Ever since I first saw you I've hoped we could meet up. -You've just got such a nice face."

And there he was, hoping she might mention his fabulous body. But still. "So have you," he said truthfully. "Your eyes are... stunning."

They exchanged smiles over the rims of their drinks.

There was a roar from the crowd and inside the pub, the band started up: the unmistakable opening chords of Motorcycle Emptiness.

"Takes me back," said John, craning his neck to get a look.

"To a good time?"

"I was in the army, loads of mates, good pay and plenty of, ah, opportunities. Yeah, it was a very good time." It came out more wistful than he'd meant.

Theresa smiled broadly. "Shall we go in?"

They stood outside the pub as it emptied out at closing time. John hesitated on the pavement, the raucous crowd flowing around them.

Theresa stepped closer to him and said, "Thanks for a great evening, John." She gave him a warm hug, then lingered, arms still wrapped round his waist.

There could be no doubt. She turned her face up to him. John slid his arms round her and bent to kiss her. She gripped him tightly then, and returned his kiss with such passion that he wobbled. They broke apart, laughing

"Whew," John said. "Snogging in the street. I'm fifteen again."

Someone whistled at them as he kissed her again more deeply, his hands travelling over her shoulders and into the small of her back. She followed suit, caressing the nape of his neck and slipping one hand into the back pocket of his jeans. His skin tingled deliciously.

"Get a room," said one of the punters coming out of the pub.

"That's not a terrible idea," Theresa said, tracing John's jawline with one finger.

John squeezed her. "I'm seriously tempted, but I'm not a first date kind of guy."

She gave a wicked laugh. "You do know that only makes you more appealing."

"Yup." She was running her fingers lightly over his back, inside his shirt."You know what they say: make 'em laugh, make 'em cry, make 'em wait."

"You devil you. Let's share a cab, I can drop you off."

When they reached Baker Street the windows of the flat were dark. John looked at his phone. Nothing from Sherlock. "D'you wanna come in for a coffee?" he asked.

"Yes please. " Her hand had been on his inner thigh since Euston.

They did at least make it as far as switching on the lights and putting the kettle on, John reflected as ten minutes later he lay on the sofa with Theresa still clenched in an embrace which had lasted since he went to get the cups out. Now he was unbuttoning her shirt as she fumbled with his belt.

"We should go to my room," he mumbled, his face in her neck.

"Ok," she said, making no attempt to sit up, or stop undoing his jeans.

The front door opened. "John, I've seen the most remarkable -"

Sherlock stopped dead, his coat-tails swirling around him. His face registered shock, then immediately, nothing.

John winced and scrabbled to sit upright. "Sherlock -"

Theresa started fastening her shirt.

"I didn't mean to interrupt," said Sherlock. His face was dark but his tone was completely neutral. "I'm going to bed. Goodnight."

He swept across the lounge and into his room, slamming the door.

Author's note: Empty vessel -I have just invented this psychological practice so any real doctors out there, please bear with me if it is nonsense!