sᴀᴛᴜʀᴅᴀʏ 8:00 ᴘᴍ

Mycroft sat alone in the room he claimed for himself at the safe house. Between two fingers he absently spun a pen, twirling it as he waited for an update from his forensic unit who was currently running a test to see if the fingerprint from the new evidence matched Millie's.

Ten minutes passed and two knocks sounded on the door. Mycroft straightened in his chair and called out, "Come in."

The woman who entered wasn't anyone who was on his team. He raised a brow, silently running his eyes over her as she stood awkwardly in the doorway; then her face clicked. The task he'd assigned to the woman had faded to the back of his mind, and due to the current state of things with his sister he wasn't very interested in what it had to say.

"Ms. Walsh. How did you find me?"

Ms. Walsh gave a tight smile. "I asked your secretary. Here," Mycroft took the manilla envelope he was offered, simultaneously creating a mental note to find a new secretary.

"Thank you. If that's all?" He gestured toward the door. The woman gave a hurried goodbye and promptly left.

Mycroft placed the thin folder on the desk, his hand gingerly hovering over it. It was Sherlock who had made him investigate their sister's whereabouts before her arriving in London; Mycroft believed his brother to be paranoid and certainly after Millie's kidnapping he would never have thought twice about…

His thoughts trailed off to the past. To a time when Eurus was around and her and Margaret were thick as thieves. Then something happened between Eurus and Margaret that changed them both. It was after Victor Trevor yet before the burning of the family mansion.

The pair of them went out for a walk one day and disappeared for two nights. Eurus returned alone, and Margaret was discovered unconscious in a bed of leaves. Throughout the following month, Margaret had a range of episodes and was thus placed on an antipsychotic; and Eurus quietly spiraled.

Both sisters were silent on what exactly occurred those days in the woods.

In the present, was it possible that Margaret stopped taking her medication? Mycroft never remembered his sister to be violent, but could she have developed new symptoms or another disorder?

Mycroft's fingertips slid forward and pulled open the folder. Inside were two sheets of paper. The first was a still from a security camera in the London Underground with a timestamp from four months ago. A red circle highlighted an image in the black and white photo; a woman deboarding a train. Mycroft reluctantly looked to the bottom of the page where a different, clearer picture was depicted of the same woman who in this image bore a striking resemblance to Margaret. The final page was a typed report from Ms. Walsh. She wrote that she used facial recognition against the second image from the Underground and it matched Margaret. It's confirmed that Margaret arrived in London four months ago.

Confusion webbed his mind as he tried to fill in the missing pieces to the puzzle. Why had Margaret not come to them sooner? Where had she been during those four months?

Four months.

An unsettling thought occurred to Mycroft. Four months ago was around when the killings began. Was it possible that a mentally unstable Margaret arrived in London and for some reason was the one doing this? The longer he mulled it over the easier the pieces fit into place. It made sense for Margaret to be Sherlock's impossible-to-catch adversary. She was smart, by staying close to Sherlock she had that advantage of always staying one step ahead.

Thinking of Sherlock caused Mycroft to feel worried for his little brother. Margaret's twisted game caused Sherlock's life to go into utter disarray. Once he learns it was the person he was desperately trying to save who was pulling the strings...

Mycroft shook his head, his voice coming out as a disappointed whisper, "Margaret,"

A/n I actually wasn't going to mention Eurus in here but there's some of Margaret's background info as to why she's like that!

And Mysteryman13 you called the twist with your other review! I wanted to respond to it but I didn't want to spoil anything haha.