about midnight
But he was lying on the floor surveying the office of Mon. . Imbert . During those five evenings , the favorable opportunity that he awaited did not take place . He left the house about midnight by a side door to which he held the key . But on the sixth day , he learned that the Imberts , actuated by the malevolent insinuations of their enemies , proposed to make an inventory of the contents of the safe . `` They will do it to-night , '' thought Lupin . And truly , after dinner , Imbert and his wife retired to the office and commenced to examine the books of account and the securities contained in the safe .