E. W. Hornung 
Thousandth Woman [EPUB ebook] 

Excerpt: "Cazalet sat up so suddenly that his head hit the woodwork over the upper berth. His own voice still rang in his startled ears. He wondered how much he had said, and how far it could have carried above the throb of the liner’s screws and the mighty pounding of the water against her plates. Then his assembling senses coupled the light in the cabin with his own clear recollection of having switched it off before turning over. And then he remembered how he had been left behind at Naples, and rejoined the Kaiser Fritz at Genoa, only to find that he no longer had a cabin to himself."