When the party returned to the block where the Overtop theory was to be tested, Mr. Quigg's services were found invaluable. He had not only been the principal grocer in the vicinity for five years, but he had served on Ward Committees for the relief of the poor at other people's expense, and had participated largely in those admirable institutions for the promotion of matrimony known as Sociables. Therefore, Quigg knew about everybody on the block worth knowing. There were a few persons in that old house near the corner, who sent in for herrings, cheap butter, and pounds of flour, and whom, of course, he did not know. There was a queer old Dutchman in that square, old-fashioned house in the middle of the block, whom neither he nor anybody else knew. They went through half of the south side of the block, and found only plain and commonplace people. Overtop and Maltboy began to be weary. The former was gradually discovering that his theory was a bore. The latter wondered whether Quigg knew the tall girl, concerning the identity of the front part of whose residence Maltboy was at fault, although he knew every brick of the rear. "In this 'ere house," said Quigg, "I shall be treated rudely, because they owe me fifty dollars for groceries. It's a curious fact, but I have noticed that debtors always act kind o' cold to creditors, as if it was the creditors that owed the money." Mr. Quigg spoke with an important air, as if he had made an original discovery in human nature. CHAPTER VI. SOMETHING HIDDEN. While this exploring party were going through the block, Mr. Marcus Wilkeson dressed himself with more than usual care, preparatory to a call upon the unknown old gentleman over the way, who that very morning had appeared at his window, the first time in three days, and tendered the compliments of the season in two low bows and a smile. Having carefully adjusted his necktie, and smoothed the creases of his gloves, Mr. Wilkeson grasped his old friend, a hickory cane, by its sturdy elbow, and marched forth to make his solitary visit. As 'he turned the corner of the street upon which the unknown old gentleman's residence was situated, thinking of the oddity of the call he was about to make, and half inclined to abandon it, he saw, in a doorway a few yards in front of him, a little girl who bore a striking resemblance to the patient creature that he had often noticed sitting at a window in the room of the pale mechanic. A single glance at the cracked and dirty front of the building established its connection with the weather-stained and shaky rear premises in which the worker toiled at his strange task from morning to night, and far into the morning again. The little girl was earnestly talking with a rough, hungry-looking fellow in a greasy cap and tattered blue overalls. As Marcus approached, he heard the following fragment of conversation: