The black envelope appears on Eliza's windowsill at dawn, though the window was locked. It smells faintly of smoke.
Inside: "The key is under the third stone. Midnight. Do not bring a light."
She recalls her grandmother's warning never to go near Blackwood Hill, where the manor watches the valley with its hollow windows. But when she tries to burn the letter, it refuses to burn. The message clings to her thoughts all day.