The wooden box was accidentally knocked open, and everyone came to look at it curiously.
This was grandma's thing. Grandpa had never been able to find the key to it and was reluctant to break it, so he kept it by the bedside as if he were protecting it.
If it hadn't been that it had become worn out over the years, or if it hadn't been for the cleaning of grandfather's belongings, everyone wouldn't have known that there was a long, long story hidden in it.