Ned and Nancy track down a ghostly saboteur in the twenty-third book in the Nancy Drew Diaries series, a fresh approach to a classic series. Nancy and Ned are visiting Coffin Hall, an estate turned rare books library, doing research on the library's rumored ghost for an episode of the NedTalks podcast when a fire breaks out in the records room. One of the library's security guards accuses Ned of arson—after all, he was the only one in the room when the fire started—but Ned swears it wasn't him. He was trying to stop the fire. He tells Nancy he saw a lady in blue right before the incident, and thinks it was Henrietta Coffin, the ghost of Coffin Hall! Nancy is confident her boyfriend is innocent, and she's determined to identify the real culprit, though she's pretty sure it wasn't of the paranormal sort. When she investigates further, she learns that the fire was just the latest in a string of recent strange and inexplicable incidents plaguing Coffin Hall. It's increasingly apparent that someone has more than a passing interest in shutting down the library. But who—or what—is responsible? And why?