As soon as Jeff Hope gasped out the name 'Moriarty', Sherlock knew he was in trouble.
Jim Moriarty, the self-styled Consulting Criminal, was no stranger to the detective. Their pasts were intertwined so tightly that Sherlock had virtually grown up with the man at one point.
It had all started with Mycroft leaving for university, a moment that changed both Holmes brothers' lives.
"I'll be back at Christmas. It really is just a few weeks, little brother. You'll barely notice me being gone." Mycroft attempted to soothe his younger brother, who was incredibly upset that his beloved older brother was leaving him alone.
"Christmas is months away, Mycroft! Who is going to drive me to the library?" Sherlock demanded with a pout.
"Both Mummy and Father can drive, Sherlock. The bus is an option too." Mycroft pointed out with a sigh, "I will just be a phone call away."
"Leave your brother alone now, Sherlock. He needs to go now or he won't reach Oxford before nightfall." Mummy said, virtually pulling the two brothers apart as she embraced her eldest son, "Be careful, Mycroft. If there's anything you need, anything at all, then please call."
"Yes, Mummy." Mycroft replied, allowing himself a moment of sentiment before he stepped out of the hug.
"Bye then." Sherlock said, glaring at Mycroft and not making any move to hug him or shake his hand.
"Goodbye, Sherlock." Mycroft replied with a nod, "Goodbye Mummy, Father. I'll be home for Christmas."
Mycroft climbed into his car and drove away, tooting the horn a little as he left the driveway.
"Honestly Sherlock, there's no need to be so unkind to your brother. University is a natural step and we should all be very proud of Mycroft." Mummy said before she made her way back into the house.
As promised, Mycroft returned from Oxford for Christmas. But he wasn't alone.
Sherlock continued to hold a grudge against Mycroft for leaving in the first place and refused to come downstairs to greet him. He watched Mycroft's car arrive and his brother climb out of the car. His eyes widened slightly when another boy got out of the car too. He was tall with dark hair and sharp eyes and Sherlock didn't like the look of him.
Mummy rushed out of the house to greet her eldest, pulling him into a tight hug before she greeted the other boy in an equally familiar way.
Sherlock turned away from the window, listening to the sounds downstairs as Mycroft's return was met with a flurry of activity and noise.
"Sherlock! Sherlock, come down here this instant!" Mummy ordered, her tone sharp as she called up the stairs to her youngest.
Sherlock rolled his eyes and trudged out of his bedroom, reluctantly making his way downstairs.
"Hi Sherlock, how are you?" Mycroft asked with a smile when his little brother appeared in the kitchen.
Sherlock ignored his brother and focused his attention on the stranger instead, "Who are you?" he asked.
"Sherlock, don't be so rude to Mycroft's friend." Mummy reprimanded as she made cups of tea.
"It's alright, Mrs Holmes." the boy said, stepping closer to the youngest Holmes and offering his hand, "My name is James Moriarty, but you can call me Jim."
Sherlock studied the man for a moment before he shook his hand, determined to get Mummy off his back. Since Mycroft had left, he'd had no buffer to protect him from Mummy's tellings off.
"You study Maths." Sherlock stated.
"Yes, I do. I've always preferred numbers over letters." Jim replied with a chuckle.
"Mycroft prefers words." Sherlock replied before he left the room.
Later, once the tea had been drunk and Jim had retired to Mycroft's room to freshen up, Sherlock sat on the stairs and listened to Mycroft talk to their parents. Even though he still held a grudge against his brother, he couldn't deny that it was reassuring to have Mycroft back. The house had felt empty and too quiet without him.
"I hope James staying with us is acceptable." Mycroft said, his tone revealing his nerves.
"Oh Mycroft, were you worried that we would reject you?" Mummy asked sadly.
"We have never discussed my interests." Mycroft admitted.
"As long as you are happy then we are happy. I know you value your privacy and enjoy your secrecy so I wouldn't dare to interrogate you about your feelings." Mummy said gently, "Mycroft, if you and James are friends then that's fine, and if you're more than friends then that is fine too."
"Thank you, Mummy." Mycroft replied, his tone much more calm.
"James seems like a decent lad." Father said, "I'm making a casserole for dinner, will he eat that?"
Mycroft chuckled, "Yes, Father. James has no allergies and will quite happily have your casserole."
Sherlock sat back a little on the stairs and considered the conversation he'd overheard. It wasn't a shock to him that Mycroft had brought a boy home. He was more shocked that Mycroft had brought anyone home at all.
"Snooping, are you?" Jim whispered, his breath tickling the back of Sherlock's neck.
Sherlock jumped, not realising that the older boy was right behind him. "No, just sitting." he replied defensively.
Jim chuckled and raised his hands in a surrender motion, "No need to get snarky. Nothing wrong with a bit of snooping." he said.
"That's not what Mummy says. She says that snooping is wrong and rude." Sherlock replied.
"Your Mum is right, but snooping also has its benefits." Jim replied with a slight shrug, "How about we make a deal?"
"What kind of deal?" Sherlock asked with a frown.
"The type where both parties benefit." Jim replied with a wink, "Here's what I propose: if I don't tell your Mum and Dad and Myc that you were snooping, then you have to tell me a secret."