Folk Ghost Stories: the Basement That Cannot Be Opened

Our old house has a basement that must not be opened. Every time I pass by that iron door, I can hear the sound of nails scratching on the door. Before she died, my grandma gave me a copper key: "Remember, what is locked underneath..." To this day, when there was a power outage on a rainy night, my daughter's voice came from the basement: "Mom, I'm so cold, please let me in." And my daughter is sleeping in the bed next to me right now.