The Gentleman in Black is a two-act comic opera written in 1870 with a libretto by W. S. Gilbert and music by Frederic Clay. The "musical comedietta" opened at the Charing Cross Theatre on 26 May 1870. It played for 26 performances, until the theatre closed at the end of the season. The plot involves body-switching, facilitated by the magical title character. It also involves two devices that Gilbert would re-use: baby-switching and a calendar oddity. Produced soon after Gilbert first met Arthur Sullivan, but before the two had collaborated, Gilbert's first full-length comic opera, The Gentleman in Black, was based on the theatrically popular theory of metempsychosis. Gilbert and Frederic Clay had collaborated previously on a one-act opera, Ages Ago. The music was not published and is now lost. The piece was never revived in Gilbert's lifetime, although modern performances have been given, some adapting Sullivan music.The libretto is included in Original Plays by W. S. Gilbert in Four Series, in the fourth volume in the series (1911) published by Chatto and Windus of London. Source: Wikipedia (en)