The Libretto
The subject for the opera was suggested to the composer by Mily Balakirev, who also orchestrated certain passages of the opera, as did Nikolai Rimsky-Korsakov.
The libretto of the opera was adapted by the composer from Vasily Zhukovsky's Russian verse translation of the like-named tragedy by Heinrich Heine, with some additional verses by Viktor Krylov, who had already written the libretti for Cui's operas Prisoner of the Caucasus and The Mandarin's Son. (The same play has been used for other operas, most notably Pietro Mascagni's Guglielmo Ratcliff, which premiered over a quarter century later.)
The action takes place in Scotland, during the 17th century (Heine's original was set in Scotland of his own time).
Read more about this topic: William Ratcliff (Cui)