Milly Darrell isn't the narrator, but the story is based around her. Mary Crofton is a new governess who meets her in school, and agrees to spend her vacation with Milly. She soon has to deal with the intrigues of Milly's evil stepmother Augusta and possessive cousin Julian. Fortunately, Mary figures out that Milly is being poisoned thanks to noticing the wrong cork on a medicine bottle. Augusta's no Lady Audley.