She wanted to know what was inside the box
She was confused by the scene because she knew her husband wasn’t rich. Why would he own a key for such a place, then? She wanted to know what was in the box, and why he hadn’t told her about the place. She was afraid to open the box, but curiosity was eating her inside. This could be something related to his ancestors, or it could be something valuable that he does not want to share. It’s been over 50 years since the secret was kept. That is a long time to keep a secret.
