20 years earlier.
Mycroft walked into the Government offices with his head held high as he strode up the steps of the building and into his first day as James Moriarty's assistant. It was a day that both Mycroft and his father had spent much time preparing for. Everything led to this day: the day when Mycroft Holmes joined his father in serving the Crown.
As Mycroft, dressed in his finest Savile Row suit and swinging his umbrella, followed father out of the house, even the young Sherlock looked proud (Sherlock was more interested in becoming a pirate than a boring government drone, of course).
As the months and years went by, Mycroft garnered great respect from his fellow employees, none more so than from James Moriarty Sr. himself. Moriarty had been impressed by Mycroft's passion for the work and often drew on their collective knowledge and intelligence. Moriarty had said time and time again that Mycroft would go far, and the two soon became peers, rather than mentor and apprentice.
Mycroft felt honoured to work with a man who he both admired and respected, and that is why, when things started to go wrong, it caused so much upset.
For several weeks, Mycroft had been noticing discrepancies in bookkeeping, altered reports and misreported events. At first, fearing a clerical error by one of the lower-positioned clerks, he approached Moriarty with documents and evidence. Moriarty's reaction had been alarming: dismissing it with a mere wave of the hand as being unimportant and to just "leave well alone".
Mycroft was increasingly perturbed by this behaviour and soon became suspicious of his mentor's own involvement. He debated discussing it with father but, not wanting to find himself in a position where somebody else made the discoveries and Mycroft himself became suspected, he decided against it and instead took it straight to a higher authority.
Large scale (but very hush-hush!) investigations were launched and, within weeks, Moriarty had vanished completely and Mycroft found himself occupying his old mentor's office full-time.
Father crowed proudly about how well his eldest son had done, and Mycroft tried very hard to be pleased himself.
Present Day.
Mycroft had poured himself a stiff drink and just sat himself back down in his Government office when his phone buzzed with a message.
Call off the reinforcements, Mr Holmes. Let's get reacquainted. Answer your next call. JM
Mycroft frowned at his phone. JM? He only knew of one "JM", and Jim Moriarty was long since dead and gone (he had ensured it himself - insisting on seeing the body and personally overseeing the cremation).
He hadn't got any further with his thoughts when the phone rang.
"Mycroft Holmes", he announced sharply.
There was a short period of quiet before anybody responded.
"Mr Holmes," a calm voice replied. "It is indeed a pleasure to hear your voice."
Mycroft's heart stopped. He knew this voice. He knew it well. Suddenly, everything came together as though all the missing pieces of the puzzle had just been handed to him on a plate.
JM. James Moriarty Sr. His old mentor and friend. Father of Jim Moriarty. Still alive after all these years.
Mycroft Holmes, for one of the first times in his life, actually felt fear. Genuine, crippling, undeniable fear.
"Mr Holmes." the voice continued. "If you ever want to see your brother and his charming doctor friend again, I suggest you call off your reinforcements and come and join the party."
"You have one hour," he continued, "You know where. And no funny business, Mycroft." He spoke Mycroft's name with a tone of almost affection. An unsettling, disquieting care that made Mycroft shudder.
The line clicked as the call ended, and Mycroft was left in an eerie silence.
Flicking through his contacts, he sent a couple of quick messages cancelling Greg's car and the armed men who had been arranged.
He picked up his intercom phone and dialled out.
"Anthea," he began, "Please send my car."
