It's the start of Mycroft's first term at Harrow. The family has moved Mycroft into his room at Bradbys House, met his roommate, and toured the campus. Father shakes Mycroft's hand, reminds him of the Holmes family tradition at Harrow and tells him to make him proud. Mummy kisses Mycroft on top of his head and tells him to be good.
"Give your brother a hug, Sherlock, it's time to go," Mummy says gently.
"I don't get to stay?"
"Not yet. You'll go to Harrow when you're 13."
Father grumbles, "Come now, son, we discussed this."
Sherlock hugs Mycroft and the older boy awkwardly returns the embrace. Mycroft notices Sherlock's pained expression and whispers, "Don't get sad in front of Father. You know how much he hates that."
Sherlock blinks, tries to change his expression to a happy one and solemnly nods at Mycroft. After the boys let go of each other, Mummy and Father load Sherlock into the car and drive off. Sherlock's greatest fear is that Mycroft won't really come back.