The Private Patient by P. D. James

When the notorious investigative journalist, Rhoda Gradwyn, books into Mr. Chandler-Powell's private clinic in Dorset for the removal of a disfiguring, long-standing facial scar, she has every prospect of a successful operation by a distinguished surgeon, a week's peaceful convalescence in one of Dorset's most beautiful manor houses and the beginning of a new life. She will never leave Cheverell Manor alive. When Adam Dalgliesh and his team are called in to investigate the murder - and a second death occurs - even more complicated problems than the question of innocence or guilt arise.