When Sherlock returned from Mycroft's office, he was pale and silent, features set in a deeply troubled expression.

John expected him to retreat to his room, or just to ignore him completely. Sherlock did neither. He sat down in his usual chair, looking up and meeting John's worried gaze.
"Are you alright, John?" He asked, so quietly John almost missed it.

He knew he meant had he calmed down, from the level of anger he must have felt to have assaulted Sherlock's brother. John nodded mutely.

Sherlock lapsed into thoughtful silence. John let it lie for a few minutes, before he questioned warily.
"Is Mycroft alright?"

There was another pause before, to John's surprise, Sherlock shook his head.
"I don't know."

Sherlock caught the look of shock on John's face and shook his head again.
"He's not injured, just bruised, but if he'd cared about that, believe me, he'd have stopped you."

Guilt was beginning to bubble and with it, John was getting angry again. He was right to be mad at Mycroft. He would never forgive the elder Holmes for his betrayal, especially now he knew Mycroft, unlike him, had not spent three years pointlessly grieving. Perhaps, he should not have unleashed his anger in such a manner, but walking past some official looking offices just as Mycroft was leaving, had been entirely unexpected. Mycroft had stopped, stared at him, read the inexorable fury in his eyes and quietly double backed, inviting John to join him.

"Sherlock…" John started, despite his feeling of vindication, needing to explain himself. "…I shouldn't have hit him. I'm sorry."

Sherlock cocked his head at him, questioning. John's eyes narrowed in sudden anger once more.
"To you." He clarified. He was not sorry for Mycroft, in the slightest.

Sherlock smiled humourlessly and nodded.

"Don't be, John, it wasn't your mistake." He replied slowly. "It wasn't Mycroft's either, I'm afraid." He added, sounding regretful.

John frowned, confused as Sherlock paused again, still thinking.
"What does that mean?" He prodded, becoming impatient in his unease.

Sherlock looked at him straight, no hint of admonishment, just guilt, in voice.
… "I told you I knew before my suicide, what I'd have to do to stop Moriarty. It never occurred to me to explain precisely, how much was planned in advance."

John was still confused, unsure what Sherlock was trying to say. He shuddered inwardly at the memory of the night at St Barts, the much more recent day of Sherlock's return from the dead.

"Mycroft gave Moriarty my life story." Sherlock stated, still looking at John directly, discouraging the look of disgust John felt he would have given the statement. "But he did so because I told him to. Because we both knew the only way to beat Moriarty, was to let him think he'd won."

John's frown deepened, mouth opening in confusion, a half formed protest on his lips. He remembered Mycroft's feeble apology, all those years ago, when John and Sherlock were still running from the police. There had never been any question, Mycroft had done wrong, it had just taken an inordinately long time for John to get truly angry about it.

Sherlock went on before John could interrupt.
"After the incident at the pool, Mycroft was spooked. Moriarty had gotten through his surveillance undetected. Mycroft used the Adler case as an excuse to arrest and interrogate him. Moriarty's fixation on me was made abundantly clear."

Sherlock paused, examining his nails. "Mycroft, came to me and…pleaded with me, to run and hide, essentially. In the end, I convinced him it was too late for that. I told him he had to feed Moriarty information on me, then release him, to give us a chance of bringing him to trial."

John had stopped listening. At least, he'd stopped registering Sherlock's actual words, while he stared at him in uncomprehending horror.

Sherlock took a deep breath.
"We knew there was a good chance the trial would fail, Moriarty's power was obvious by then. It was also becoming clear he and his people would not stop, until I was dead, whoever they had to go through to get there. It didn't take a genius to know I had to die. Luckily, we had two geniuses. Between us we worked out a way for it not to be permanent."

John continued to stare in silence.

"When I came back, you guessed it was Mycroft who guided the rather flattering press reports, clearing my name. What you couldn't be expected to know was that all this time, I'd been forgetting to return the favour."