Murder at Monte Carlo by E. Phillips Oppenheim

Roger followed the man along that dreary carpeted way which he was beginning to loathe, mounted in the lift by the side of which Luke Cheyne had been murdered, crossed the lounge of the Hôtel de Paris, left by the swing doors and went up the steps into the Casino. Here his guide led him by a devious way to an underground floor and paused before a door guarded by a gendarme. They were allowed to pass in, however, and found Thornton engaged with one of the Monaco officials, a solemn-visaged doctor and an undertaker. Upon a mattress, raised a little from the floor and covered over with a sheet, was the victim of the tragedy. Thornton disengaged himself from the others and came over at once to Roger. It was obvious that he had received a shock, for his eyes seemed to have receded farther into his head than ever. He was very pale and had lost something of his cold equanimity of manner.

"Sloane," he exclaimed, "this is damnable!"