Sherlock's head felt like it was about to split in two. He knew this feeling, although it hadn't happened quite this badly in more than a year. He had sequestered himself in his room with the lights off and the shades drawn so that not even the smallest bit of light from the abominably cheerful sun (why did it actually have to be sunny, today of all days?) outside could get in. John was trying to be quiet, but Sherlock felt like every sound was multiplied ten, an hundred, a thousand times until even the sound of his own breathing made it feel as if someone was using his head for a timpani drum.
John had asked three times over the past two hours if there was anything he could do. Sherlock sent him away each time, knowing that nothing John could do would do any good at all.
Finally, after John's fourth try, Sherlock texted Mycroft. Even the small light from his phone sent daggers through his brain.
Half of an eternity of an hour later, he heard footsteps outside of his door. The small tap of Mycroft's umbrella being propped against the wall made Sherlock flinch.
"You should have called me straight away," Mycroft said softly as he entered.
"Thought it would stop," Sherlock mumbled, trying to be both nearly silent but still audible. He heard the slip of fabric on fabric as Mycroft removed his tie, the slight rustle of a jacket being removed, the soft slick of laces and the thud of shoes taken off. Mycroft padded around the bed so he was behind Sherlock, and the bed dipped as he climbed in.
Warm, dry hands rested against Sherlock's neck just where the base of his skull ended. Mycroft rubbed slow, gentle circles there, softly at first and then applying more pressure as the muscles relaxed.
Sherlock turned over so he was under Mycroft's arm with his head resting just under Mycroft's heart. The slow, muffled thudding was relaxing, as was the hand slowly massaging the muscles in his neck.
Slowly, as the pain faded and the tension hard muscles relaxed, Sherlock fell asleep.
Mycroft knew the instant Sherlock's headache had gone. The crease in his brother's brow had smoothed itself out. Sherlock looked ten years younger when he slept, and the memory of the nights they had spent like this as children came rushing back. Sherlock, prickly and misunderstood, had had these headaches all his life. And Mycroft had been the one who, when Sherlock was eleven, had figured out how to make them stop.
Mycroft pressed a light kiss to Sherlock's forehead and extracted himself carefully. Moving silently (a skill he'd perfected out of necessity) he put on his tie, jacket, and shoes before he let himself out of Sherlock's room.
"Is he all right?" John asked when he saw Mycroft emerge.
"He'll be fine when he wakes up," Mycroft replied. "He's had headaches like this since adolescence. He hasn't had one in several months, though, or at least he hasn't told me if he has."
"I've never seen him like that," John said. "What'd you give him?"
"The only thing I've found that works," Mycroft replied. "A bit of peace."