Mycroft, being the man he is, is always good at keeping himself detached and rational. Yet, something happened for the first time. As he kept you in company a fire ignited in his heart which only grew stronger with time. He tried to ignore it, ignore the insecurities and warmth that fire aroused.

Then came the revelation, a betrayal. You are a spy who worked against him all that time.

The disappointment in his eyes betrayed his stoic face. "I was a fool to believe in love." He whispers.