The Secret of the Night or Rouletabille and the Tsar (French: Rouletabille chez le Tsar) is a 1913 mystery novel by the French writer Gaston Leroux. It is the third in his series of novels featuring the fictional detective Joseph Rouletabille, following on from The Mystery of the Yellow Room and The Perfume of the Lady in Black.
Gaston Louis Alfred Leroux (6 May 1868[1] – 15 April 1927) was a French journalist and author of detective fiction. In the English-speaking world, he is best known for writing the novel The Phantom of the Opera (Le Fantôme de l'Opéra, 1910), which has been made into several film and stage productions of the same name, notably the 1925 film starring Lon Chaney, and Andrew Lloyd Webber's 1986 musical. His 1907 novel The Mystery of the Yellow Room is one of the most celebrated locked room mysteries.