Murder at Monte Carlo by E. Phillips Oppenheim

Roger's return to consciousness was bewildering. He found himself lying fully undressed in a pair of strange pyjamas, in a narrow but exceedingly comfortable bunk-like bed, covered with the finest of linen and a silken coverlet. The room was in complete darkness save for a heavily shaded electric lamp burning by his side. He removed the shade and his perplexity increased. The apartment in which he found himself was no larger than a ship's cabin, and the walls appeared to be of some sort of metal. The furniture was scanty--a wardrobe of gleaming mahogany let into the wall, a large toilet basin with oxidised silver fittings, and a single chair on which were stretched the clothes he had been wearing. The room was entirely windowless, but two electric fans were revolving noiselessly. He felt very sick and he had a bad headache, but both sensations almost disappeared as, with a sudden flood of memory, he remembered the events of the preceding night. He sprang out of bed, bathed his head and his body so far as possible in cold water, and rapidly dressed. The only thing missing from amongst his belongings seemed to be his revolver. He was just completing his toilet when the door of his room opened. He gave a little gasp. Thornton stood there, looking in at him!

"Say, did they get you too?" Roger exclaimed. "What became of the men you were to bring?"