Everyone is helping Mom prepare for her game show gig. Louisa gets the day's questions from the elderly people who watch TV at the nursing home where she works, Miranda copies them onto index cards, and Richard quizzes Mom.
Today, Miranda is supposed to be doing homework in her room. Instead, she's practicing untying knots (metaphor alert).
Richard got Miranda into the knot untying business because he sailed boats as a kid. Richard unties knots when he's trying to solve a problem at work.
That's exactly what Miranda is doing now. She's trying to figure out the answer to her problem, which is "you" – that pesky, unnamed person who has asked her to write a letter.
"You" asked her to write a letter about everything that happened "that day this past winter" and "everything that led up to it" (6.5).
She's not sure where to begin, that's the problem. Though if she had to, she'd say it all started with the day Sal got punched.