Part One.

Sherlock examined the body, lifting the folds of the clothing and sifting through pockets as Lestrade watched on. Donovan stood to one side, arms folded and eyes blazing with the intensity of a blue dwarf star. He ignored her, as he always did, and continued his evaluation. Finally, he stood and looked at Lestrade, looking older in the forensic team's blinding light fixtures, before noticing the girl beyond the detective inspector, standing just behind the yellow tape at the end of the alley and lit by the flashing police lights.

"One minute," he sighed, walking quickly past the grey-haired man.

"But the body—" Lestrade protested, turning to watch him.

"She followed again," he called over his shoulder, irritation thick in his tone.

Donovan snorted. "Might want to consider chaining her up when you leave the house."

Sherlock paused and turned to her. "I'm sure your lover considers the same thing when he thinks of you." Then smirking, he walked away, noticing the way her cheeks flared with heat and her lips tightened in frustration.

The girl peered past him as he approached, hoping to get a glimpse of the body, so he stood in front of her to make sure he had her attention.

"Thea Anne—how many times have I told you not to follow me when I'm called to a scene?" Sherlock asked his daughter. He was frustrated, but she didn't seem to care.

She smiled. "This month alone? Fourteen."

"So why are you here? Especially when you know Lestrade doesn't want you to be?"

Thea scoffed. "He only doesn't want me here because he's afraid I will be psychologically scarred and file a report against him. Which I would never do, since he's like an uncle to me."

"He doesn't want you here because you shouldn't be." He sighed. "You're lucky I don't call for your grandmother to come and pick you up. Maybe a week in the countryside would do you some good."

She scrunched her nose. "It's so boring out there. Grandpapa makes me sit and do a month's worth of crossword puzzles with him—says it's good for the mind, but I know it's because he thinks we bond over them." Then she muttered under her breath, "And because I'm so bloody good at them."

"Thea—"

"And besides," she interrupted, "it's not my fault you used to bring me to crime scenes all the time when I was growing up."

Sherlock rolled his eyes. "I hardly count sitting in a police cruiser with a book as 'accompaniment'. And those were only the nights that your babysitter couldn't come look after you. Look, one day you'll be able to assist me, but—"

"Sherlock!" He turned to see Lestrade looking towards them, annoyed. "Just bring her over."

Donovan looked to the DI and began to argue, but he had the final word and motioned to them. Sherlock looked back at his daughter, noticing the gleam of anticipation in her eyes, and shrugged. "Must have trailed along one too many times for him to care. Now, what are my rules?"

Thea ducked under the caution tape and stuffed her hands in her pockets, where Sherlock knew she kept her pocket magnifying glass and a notepad, just in case. "Observe but don't disturb, stay one step ahead, and think of all the possibilities before jumping to conclusions."

"And?"

"Wash your hands thoroughly after touching dead bodies?"

"Thea."

She was quiet for a second before adding, "Examine all the evidence as it presents itself. Make connections only where they appear. And of course, eliminate all other factors, and the one which remains must be the truth."

"Good girl. Now," he paused and placed a hand on her back. "If it's too much to handle, let me know. I'll take you home."

She rolled her eyes, mirroring him when she did. "Please, I've looked into all your other cases, pictures and all, and you know that. Besides, we both know you won't leave the scene."

He looked over her, a teenager of seventeen, and for the first time didn't see a little girl. She was tall now, with long, dark, curly hair like his and a slender woman's figure, complete with curves. She resembled her mother so much in her features, but she had Sherlock's brilliant blue eyes, marked with knowledge and intuition of someone so much older. He gave her a quick half-smile. "Clever one, aren't you. Let's see what you've learned over the years."

She beamed as they crossed the final few feet separating them from the body. Donovan huffed away, giving the teen a disgusted face as she passed, but Thea paid no attention; she was used to the abuse from the sergeant. Lestrade offered her a small smile and some latex gloves, a little curious himself on how well she'd do. Without another thought, Thea focused on the body in front of her, making sure she didn't miss anything so as to impress her father.

He was a younger man, early-to-mid-twenties, with short blonde hair and some scruff on his cheeks and chin from not having shaved in a while. His dark eyes were open even in death, and one of them had a burst blood vessel, probably from the impact of the gunshot wound to the back of his head. There was an exit wound in his temple, messy and still bleeding a little. Someone must have seen the murder and immediately contacted the police, though no witnesses other than passers-by on the street had been called forth. Strange. Even stranger still was that his hands were near his head, as if he'd put them up before being shot.

She examined the entrance wound on the back of his head, noticing the burn patterns around the wound itself. It'd been a contact shot, with the imprint of the barrel burned into the skin and hair surrounding it. That'd been mistake number one—she could tell clearly now what type of gun was used.

Thea, no longer worried with the cause of death, turned instead to his pockets, hoping to find some identification for the young man. His wallet was in his back pocket (typical of men) and she opened it to find an ID for London Metropolitan University with the name Isaac Taylor imprinted on the front. She showed it to Sherlock, who nodded. After finding only a tenner and a few membership cards to a gym, art shop, and nearby coffee bar, she placed the wallet in a forensic baggie and continued her search. Surmising that he was an art student at the university, Thea looked under his nails and found moulding clay—jackpot. She searched his jacket pockets and soon found a slip of paper, torn from a sketching notebook, with a number and a girl's name—"Erin". She stood and placed it in a different bag, handing it to Lestrade.

"I think I've gotten everything I need," she said, looking to her father, but she couldn't get a read of how well she'd done.

Lestrade glanced at the paper. "That was only five minutes."

Thea shrugged. "Dad did it in less. I'm still learning."

"So who did it and why?" Sherlock asked, his hands still in his pockets and his eyes curious.

She smiled widely, looking very much like her mother. "The ex-boyfriend."

"What?" Lestrade asked, examining the paper in the bag again. "But how—?"

Thea strode to the other side of the body, pointing things out as she went. "Obviously you know the model of the gun because it's imprinted on the back of dear Isaac's head, and it was a contact shot because of the star-shaped hole. I'm assuming the bullet is somewhere a little farther down the alley—and I'm sure dear Anderson could fetch it for you if you asked nicely—and he died instantly. His wallet shows he's a student at the London Met, more specifically an art major since he has clay under his nails, membership cards from the art supplies store and coffee bar near the university, and wears clothes from the men's section of Forever 21." She looked up at Lestrade. "Typical hipster art student fashion. The number in your hands is torn from a notebook, more specifically from an art student's sketchbook because on the other side is a small part of a larger sketch. I'm sure if you can find Erin, you'll find the page she tore it from. But she's not important—her ex is."

Sherlock tore off his gloves. "And why is it the ex?"

Thea rolled her eyes. "There are only three men in a girl's life who would kill another guy for her: her brother, her father, and her crazy ex. Since the gunshot wound was a contact one and because the death was simply over Isaac getting Erin's number, the latter is the most likely. Find Erin and you'll no doubt find her jealousy-filled ex. Girls love to talk about that sort of thing." Her eyebrows knit together as she glanced around at the buildings above them. "Though there's one part of it that seems rather strange to me—the call to the department was fairly soon after the murder but there's no suspect and the windows around the alley don't have a good enough view of the scene." She looked expectantly to her father.

Sherlock nodded curtly. "I'd wondered if you'd catch it. No matter, that was a tough one." Regarding Lestrade, he added, "You might want to arrest Erin, as well. It was a set-up."

The teen's eyes lit up while Lestrade looked blankly at the consulting detective. "And why do you think that?'

"Clever. Absolutely abhorrent but clever," Thea mused, "She knew him somehow, probably through one of her friends, figured he'd done something horrid, and set up a plan for her boyfriend to kill him. What better reason than that Isaac was flirting with his girlfriend? She followed to make sure his reaction would be as she'd predicted, then felt guilty and called the police."

Lestrade placed a hand on his forehead, as if trying to keep the information together. "So, we arrest Erin and her boyfriend? There's no ex?"

"Correct," she replied, taking off her gloves and clasping her hands behind her back, "That bit was my fault, I hadn't considered the possibility of the caller being so involved in the murder."

Sherlock gave her one of his infamous smirks and motioned for her to follow him. "If we're finished, I'll bid you goodnight, Detective Inspector." Thea stepped over Isaac's body and walked away from the scene with her father, occasionally glancing up at him and trying to hide a smile.

"Stop doing that, you might as well be happy. You did well for that being your first case," Sherlock complimented, a rare occurrence that sent her into a small fit of giggles.

"Except I didn't catch everything. If I'd actually examined everything, I would've thought of her motive rather than his."

"Mistakes happen. As long as I'm there to catch them, you won't have to worry."

She stopped. "But you won't always be there, will you?" It hadn't been a question.

Sherlock stopped and stood in front of her, placing his hands on her shoulders. "I know I'm not a great father, but I'm trying. I promised your mother I would always watch over you and I haven't broken it yet."

Thea placed one of her hands over his and offered a half-smile. Then she took his arm and placed it over her neck, leading them to the street so they could call a taxi and go home. Then it dawned on her.

"Oh. Dad. Erm, there's something you should know…"

He looked to her. "Your tone implies it's not good news."

She shook her head. "No. It's not. Our landlord came down and told me we needed to leave. Other tenants are beginning to complain about the experiments, your clients, and the noise. He's given us a couple weeks to find another place but..." Her father sighed and she leaned into him.

"We'll find a way, Thea. We always do."