Note: Originally published by William Collins Sons & Co., Ltd. in England in 1975 as by "Harriet Esmond" (info from copyright page of Delacorte edition on archive.org). According to "St. James Guide to Horror, Ghost and Gothic Writers" (via Wikipedia), this was a joint pseudonym used by the horror author John Burke and his wife Jean Burke. The 2017-2018 editions were as by John Burke alone. Additional clarification of Jean Burke's role is needed.