about eleven o’clock
`` No , I should n't , '' said Thaddeus `` we 'll pass you off as a business acquaintance of mine up from town , and you can stay all night and watch developments . '' So it was arranged . The detective was introduced into the family as a correspondent of Thaddeus 's firm , and he settled down to watch the household . Afternoon and evening went by without developments , and at about eleven o'clock every light in the house was extinguished , and the whole family , from the head of the house to the cook , had apparently retired . At half-past eleven , however , there were decided signs of life within the walls of Thaddeus 's home . The clew was working satisfactorily , and the complete revelation of the mystery was close at hand . The remainder of the narrative can best be told in the words of the detective : `` When Mr. Perkins sent for me , '' he said , `` and told me all that had happened , I made up my mind that he had a servant in his house for whom the police had been on the lookout for some time .