P. D. James 
Skull Beneath the Skin 

Fading star Clarissa Lisle plans a spectacular comeback in a private performance of Websters bloodcurdling tragedy The Duchess of Malfi, to be staged in an island castle owned by the eccentric collector Ambrose Gorringe. When she begins to receive poison-pen letters bearing death threats couched in Shakespearean quotations her husband hires young private detective Cordelia Gray to ensure her safety.But before the curtain rises, one of the party will fall victim to a murderous blow, and as the suspense builds, it becomes clear to Cordelia that everyone confined within the walls of the castle seems to have an excellent motive for sending Clarissa Lisle down, down to hell.From the Paperback edition.