The After House (Musaicum Vintage Mysteries). Mary Roberts Rinehart

Ralph Leslie, a young doctor by professor, signs on as a private helper on a yacht. Soon the yacht is rocked with sensational triple axe-murders and Leslie is the only person who can inspire trust in the crew. But who is the killer? How will he get caught now? Excerpt: "The yacht Ella lay in the river not far from my hospital windows. She was not a yacht when I first saw her, nor at any time, technically, unless I use the word in the broad sense of a pleasure-boat. She was a two-master, and, when I saw her first, as dirty and disreputable as are most coasting-vessels. Her rejuvenation was the history of my convalescence. On the day she stood forth in her first coat of white paint, I exchanged my dressing-gown for clothing that, however loosely it hung, was still clothing. Her new sails marked my promotion to beefsteak, her brass rails and awnings my first independent excursion up and down the corridor outside my door, and, incidentally, my return to a collar and tie."