Mary is a young woman  in victorian London. A former prostitute, she gave it up after falling in love with Robert. His jealousy and suspicions about her past lead him to become the Ripper, ultimately making Mary his last victim.

Mary is the emotional heart of the show and the story is told through her eyes. In this song, she has discovered Robert's true nature, and though she loves him, she vows to stop him killing again, even if it kills her.