Have His Carcase
Dorothy L. Sayers
 During a hiking holiday after her acquittal on murder charges in Strong Poison, Harriet Vane discovers the body of a man, with his throat cut and the blood still liquid, on an isolated rock on the shore. There are no footprints in the sand other than the man's and Harriet's. She takes photos and preserves some evidence, but the corpse is washed away before she can fetch help. Lord Peter arrives, and he and Harriet make investigations alongside the police. The dead man, Paul Alexis, a professional dancing partner at the local hotel, was of Russian extraction and engaged to a rich older widow. The death has been made to look like suicide, but Wimsey and Harriet discover that he was the victim of an ingenious and complex murder plot. The romantic Alexis believed himself a descendant of Russian royalty, and the widow's rather stupid son, appalled at the prospect of his mother's remarriage to a gigolo and the loss of his inheritance, conspired with a friend and his wife to play on Alexis's fantasies. Convinced that he was being called to return to Russia in triumph as the rightful Tsar, Alexis was lured to the rock and murdered by the son, who rode a horse along the beach through the incoming tide to avoid leaving tracks, whilst his friends supplied his alibi. The death was intended to look like suicide. However, Alexis suffers from haemophilia, and his unclotted blood leads to confusion over the time of death, which eventually assists with the unmasking of the conspirators.