In the days that followed, Sherlock tried to find out more and more about the mysterious sender. He turned the paper over and over, examined it with a black light for hidden messages or analysed the paper's texture in the laboratory. He looked for fingerprints, DNA traces or anything else that could bring him closer to the mysterious sender.

But there was nothing to be found. This mysterious letter writer clearly knew what to look for and kept himself well undercover.

Sherlock was beginning not to know what else to try or analyse. He didn't know what he was dealing with and that bothered him immensely. Not knowing unsettled him. And the thought that (not if) something bad would happen, only more so. Again and again he wondered what the mysterious messages were all about. He rummaged through his memories and his old cases to find any clue as to what they would want him to pay for.

Sure, he had put many criminals in prison over the years, but they were mostly loners or their relatives didn't have the know-how to pull something like this off. In his opinion, they were simply too stupid not to get caught. So it had to be someone who knew how to do it. The only one who wanted to destroy him was Moriarty, but he had been taking care of that and his criminal network for the last two years. And Moriarty himself was dead. So it couldn't be him.

His thoughts then turned to a certain woman. The woman, to be more precise. Was it Irene Adler, who was now out for revenge? He had foiled her plan then and delivered her to Mycroft. However, he had also saved her from certain death. And besides, she would not stoop to such trivial methods.

So it had to be someone he had not suspected so far. Someone who had kept in the background until now.

His thoughts were interrupted when suddenly the laboratory door swung open and a small figure, pale-faced, entered.

"And Sherlock? Have you made any progress?" asked Molly as she slowly made her way in his direction.

"No nothing! No fingerprints, no fibre residue or traces of any substance. Just nothing!" he growled in exasperation.

Then he turned to her and looked at her more closely for the first time in several days. Her skin was pale, her eyes looked tired. Dark spots stood out under her eyes. She looked limp and exhausted. But as always, she wore her characteristic friendly smile on her face, which was meant to distract from her condition.

"Are you all right? You look pale. Even paler than usual?" he then asked.

"That's a nice description" she replied in a sarcastic tone, rolling her eyes.

"No, I didn't mean -"

"It's fine. And yes I'm fine. I've just been feeling so incredibly tired lately" she interrupted him holding up a hand.

Under his sceptical gaze, she finally turned to the paper in front of her and took it in her hands. Sherlock eyed her actions critically. Her gaze continued to fall on the envelope and remained there for several minutes.

Startled, she turned her head and looked wide-eyed at the person in front of her.

"I think I know this writing" she then said.

Sherlock immediately straightened up in his chair, took the envelope from her and stared likewise at his name written there in slightly illegible script.

"So, whose is it Molly's?" he asked hopefully.

But before Molly could say anything, the door swung open again and a tall young man stepped in. They both looked towards the door, startled. Sherlock sighed heavily, knowing that the moment had now passed.

"Hello Molly. Are you ready?" the man then asked as he entered the room. His eyes fixed on the two of them.

"Oh, Tom. Is it that late?" she then asked, glancing at her watch.

"I'll be right there." she said hesitantly, but made no move.

Sherlock also noticed her sudden tension and sensed that Molly did not want to leave. She knew something but something or someone was stopping her from telling.

"Molly? We really have to go now" sounded impatiently from the direction of the door.

Molly woke from her trance and turned away from Sherlock. Just as she turned to leave the lab, Sherlock grabbed her wrist. Slightly confused, she looked first at the hand around her joint and then at his face. His expression was unreadable but the grip tightened.

"Any important plans for tonight?" he asked then, looking at her urgently.

Molly swallowed hard, suddenly at a loss for words. Her whole body tingled under his touch and a slight warmth shot into her cheeks.

"We're meeting my parents for dinner and then we're going out for drinks with some friends afterwards." it replied again from the direction of the door.

Sherlock didn't even take his eyes off Mollys' the whole time Tom was talking. Then he slowly loosened his grip on her wrist and finally let her go.

"Have fun then," he said coldly, turning his gaze back to the microscope in front of him.

He heard the two of them slowly make their way out of the room and the door slam shut. Then he exhaled heavily.

Just as he was about to ask what was wrong with Molly and why she was suddenly so tense when Tom entered the room, the door swung open again.

Molly came running to him with quick steps and leaned forward slightly.

"If you want to know who wrote that letter, come to the bar tonight where we celebrated John and Mary's engagement" she whispered softly.

And as quickly as she had come, she was gone.

And Sherlock was sure that today, thanks to Molly, he was one step closer to unmasking the mysterious sender.