Magic squares are mathematical puzzles that feature in many of Marlee’s interactions with Liz. She describes the first moment she picks up Liz’s math notebook:

On the back was a square with lots of little squares in it. In some of the squares were numbers. I knew what it was—it was a magic square […] The simplest was a three-by-three square, with the numbers 1 to 9 arranged so that every row, column and diagonal added up to 15 (27).

Because of Marlee’s fascination with math, the discovery of this puzzle on the back of Liz’s notebook creates an instant bond. Marlee has just refused to be Liz’s history project partner, but seeing the magic squares changes her mind and launches their friendship. Liz uses one of her own mother’s magic square books as a reward for Marlee if she will speak before the whole class to present their project. When Liz fails to show up and Marlee presents the project alone, she sends a note to Liz saying that Liz owes her a magic book.

Even after Liz has left their school, Marlee maintains contact by insisting on receiving the promised magic book. Since their friendship is now dangerous because of the racists in Little Rock, Liz and Marlee revert to speaking in code using magic squares.