A/N: This is my second fill for the trope bingo challenge on Let's Write Sherlock. It fills the De-Aging square on my card.
Mycroft wasn't entirely sure how it had happened.
Admittedly, Sherlock had always been more than fond of experimenting, and his experiments were rarely ever harmless, but Mycroft had never expected anything like this. Only Sherlock could turn an entirely routine day into an unmitigated disaster.
Unknown to anyone (and he would need to start inspecting Baskerville personally, if his brother was able to not only break into the facility and emerge unscathed but also steal chemicals without notice), Sherlock had taken a sample of a chemical out of curiosity, taking it back to Baker Street to study it.
And, in the course of Sherlock's studying, he had somehow managed to not only ingest the chemical but had also fed it to John Watson as well. Ordinarily, with the more typical experiments that his brother ran, nothing would have come of it. The two may have lost consciousness for several hours, or had an unexplainable (unexplainable to John, as he didn't know that he was being fed an unknown chemical) rash, but that would have been the extent of the damage.
Now…he sighed, shaking his head as he looked at the two toddlers in his living room.
John Watson, age three, was frowning in concentration as he attempted to put together a puzzle of a dog, while Sherlock, age two, was writing (if the nonsensical scribbles on paper could be called 'writing') something that was more than likely a monograph about pirates or bees. Mycroft remembered his brother at age two very well, and both subjects had held Sherlock's interest until he was old enough to discover crime.
Mycroft himself was sitting in his armchair, watching the two toddlers who had been his brother and brother's friend, considering his options. For many, obvious, reasons, their families couldn't know. Harriet Watson was hardly a concern, as she was usually too inebriated to concern herself with calling her brother. Mummy and Father would be slightly more difficult, but as they were used to not hearing from Sherlock for two or three years at a time, they had time to reverse this.
Anthea had updated both men's websites, simply stating that they were in the middle of a complex case and thus unavailable to take any cases at present. It wouldn't do to have clients consulting a two year old, after all. No one had the necessary clearance to know what had happened.
That also meant, unfortunately, that the list of people who were able to take care of the two boys was very short. He had too much to do, especially with the upcoming elections in…well, he had too much to do to take care of two toddlers. He needed to find someone he trusted to do so, however, which only left him with two options.
"You want me to what?" Anthea asked, looking from her boss to the two toddlers who were currently napping, curled together like puppies.
"I do not believe that I stuttered," Mycroft replied calmly, as though this was a truly typical request. All in all, with everything she had needed to do for him over the years, this really wasn't too unbelievable.
"You want me to find a replacement for me, temporarily, while I move into your brother's flat and care for both him and Doctor Watson with the assistance of their landlady?" she asked incredulously. Still, it wasn't the oddest thing she had needed to do.
"You are the only one with the necessary clearance, and who is capable of the necessary discretion," Mycroft replied, looking at the sleeping children briefly before refocusing on his assistant. "Their landlady has been sworn to secrecy as well, but with you there it will minimize instances when she does let something slip."
"What is my cover story?" she asked. Mycroft's mind was made up, which meant that she either needed to agree, or quickly find a good counterargument. Waiting too long would just give him more time to come up with his own counterarguments.
"A single mother with two children," he answered. "Two different fathers, obviously. Mrs. Hudson was a friend of the family, and she is allowing you to stay in the flat while John and Sherlock are away, until you get back on your feet."
Anthea sighed, taking the file he handed her and looking through it. Everything had been planned out, even where she should apply for a new job. It seemed logical, but… "I know nothing about children," she protested.
"You once mentioned having four sisters, two of them younger than you," he remarked. "And all four of them have at least one child. Did you never care for any of them?"
"I am rather busy ordinarily, and have little time to be a babysitter," she said. That was ignoring the fact that she had a poor relationship with her family to begin with. "So no, I have never babysat for them."
"Think of this as practice for when you have your next family reunion," he replied, out of patience. "Anthea, you will watch over my brother and Doctor Watson with the assistance of their landlady until such time as the cure is found and can be administered."
"Is there no possibility that the landlady can watch them herself?" she asked. It was a weak argument, she knew that, but it was the last one that she had.
"If any of my brother's enemies discover his current condition, do you believe that one aging landlady would be capable of stopping them?" Mycroft enquired.
Anthea sighed. That, of course, was a valid concern. She was well equipped to deal with any threat that would arrive, but Mrs. Hudson would be unable to do so. "My assistant will be able to handle my workload temporarily, and you may send me the more classified matters that you will need my assistance for." Otherwise, she may well go mad. She wasn't the type to be a stay at home mother, although she had nothing against those who chose that option. She simply didn't have a maternal bone in her body.
Anthea shook her head as she left to go to her flat to pack her belongings. She would need to buy clothing, books, and toys for her 'children' as well.
This morning had been the start of a perfectly ordinary day. She should have known then that something was going to happen, but even then she doubted that she would have been able to guess this. Sherlock Holmes and his friend were both children and she was entrusted with their care until Mycroft was capable of finding a cure. Just another day when you worked for Mycroft Holmes.