The prologue is just for a solo singer (tenor) and piano. He tells us about a young governess he once knew who looked after two children at Bly House. The children’s parents were dead, and they were supposed to be cared for by their uncle. The uncle, who lived in London, was far too busy to care for them, and he hired a governess for them. He told the governess (who is just called “the governess” in the opera) that she must never write to him about the children. She must make any decisions about them herself. She must never ask him about the history of Bly House, and she must always continue to care for the children.