The Parker Inheritance by Varian Johnson
From Arthur A. Levine Books:
Find the path. Solve the puzzle.
When Candice finds a letter in an old attic in Lambert, South Carolina, she isn't sure she should read it. It's addressed to her grandmother, who left the town in shame. But the letter describes a young woman. An injustice that happened decades ago. A mystery enfolding the letter-writer. And the fortune that awaits the person who solves the puzzle.
So with the help of Brandon Jones, the quiet boy across the street, she begins to decipher the clues. The challenge will lead them deep into Lambert's history, full of ugly deeds, forgotten heroes, and one great love; and deeper into their own families, with their own unspoken secrets. Can they find the fortune and fulfill the letter's promise before the answers slip into the past yet again?