In the short story Swan Song, Rustonbury Castle is the historic feudal seat of the Earl of Rustonbury, located in Hertfordshire. According to Mr Cowan, the manager of opera singer Paula Nazorkoff, it is "a real dandy old feudal seat, ghosts and family pictures, and secret staircases...." One of the more interesting features of Rustonbury Castle was its own private theatre. This was built less than a hundred years ago by the present Earl's grandfather. It had become "the chief toy" of Lady Rustonbury who delighted in staging private theatrical performances there. One such private performance and what happened there would form the main plot of the story.
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