Mystery

A mystery was an unsolved secret.

Michael Jennings liked to solve mysteries. (AUDIO: The Curious Incident of the Doctor in the Night-Time) The disappearance of the Old Ones was ranked by the Time Lords as the sixth greatest mystery in the universe. (PROSE: Tomb of Valdemar)

Mystery was also a genre of fiction. Fox Soames was a mystery writer in the early 20th century. (PROSE: Mad Dogs and Englishmen) The Brenda and Effie series was a series of mystery novels by Paul Magrs. (PROSE: The Story of Fester Cat)