The Mysterious Key and What it Opened is written by L. M. Alcott. The strange passing of Sir Richard Trevlyn sets the story in the beginning. The only thing the reader is aware of is that Richard's wife, Alice, who is expecting their first child, is listening to a discussion Richard is having with a visitor via a keyhole in the library door. She faints after being horrified by what she hears, and a servant named Hester discovers her and puts her to bed. Hester rushes to the library to inform Richard that his wife is ill despite Alice's insistence that he not be disturbed. She discovers him dead, slouched over his desk. A sixteen-year-old kid named Paul who is applying for work on the estate runs into the young child, Lillian, twelve years later. He performs his duties successfully, rising in rank and winning the love of both his family and his employees. Some of the servants are confused and sad when he goes without saying goodbye since they have a suspicion that he may be more than just the gardener or groom. When everything is revealed in the final chapters, the riddles of why Richard died, who Paul is, and how those things are connected are still unsolved.