midnight
At nine o'clock he returned to Monte Carlo , and again ascended the station lift , as was his habit , for a stroll through the rooms and a chat and drink with one or other of his many friends . He looked everywhere for the Swiss pair in whom he was so interested , but in vain . Probably they had gone over to Nice to spend the evening , he thought . But as the night wore on and they did not return by the midnight train -- the arrival of which he watched -- he strolled back to the Métropole and inquired for them at the bureau of the hotel . `` M'sieur and Madame Granier left by the Mediterranean express for Paris at seven-fifteen this evening , '' replied the clerk , who knew Walter very well . `` What address did they leave ? '' he inquired , annoyed at the neat manner in which they had escaped his vigilance .