midnight
X. Alden , with his ear to the ingenious little `` electric eavesdropper , '' experienced an unpleasant chill upon hearing the visitor within addressed as `` Professor . '' He had conceived the idea that Sheard -- whom he strongly suspected , might hold interviews with the mysterious and elusive Séverac Bablon in the small hours of the morning , at his own house , when the rest of the household were retired . Mr. Alden had watched for five nights when he knew the pressman to be at home . On four of them Sheard 's light had been extinguished before midnight . To-night , the fifth , it had remained burning , and long vigilance had been rewarded . A car had drawn up at some distance from the house , and its occupant had proceeded forward on foot . He had been admitted so rapidly that Alden had been unable to ascertain by whom .