Unnatural Death

In Unnatural Death, a novel by Dorothy L. Sayers published in 1927, Lord Peter Wimsey investigates the death, three years before, of an elderly lady in the last stages of cancer. There was nothing suspicious about it, and the young doctor who had been treating her had checked and re-checked everything, because he had not thought she was so close to her end, but Lord Peter thinks there may have been something fishy about it after all.