"An agent gave his life to tell us that."
"Perhaps he shouldn’t have done. He was obviously just trying to show off."
Did anyone else notice Mycroft’s face? He’s the first to dismiss sentiment so why does he take Sherlock’s comment so hard? They also mentioned the importance of the agent’s death many times - along with Mycroft’s broken heart. Even if the latter was a joke, it makes me wonder - did Mycroft know this agent? Are we going to learn in the future that he had finally made a friend? Was this why he wanted Sherlock to quickly change the subject? If so, this would make Sherlock’s ‘How do you know’ such a terrible foreshadowing.