Vaughn bowed again, then turned away and entered the waiting carriage. The door closed with a bang. The hackman mounted to his box, caught up the reins, then drove rapidly away. The undertaker’s wagon already had departed. CHAPTER IV. WHAT DAYLIGHT REVEALED. Nick Carter found Mr. Rudolph Strickland and his niece awaiting him, but Arthur Gordon had not yet arrived. “I have talked with him by telephone, Mr. Carter, and he now is on his way here,” said Wilhelmina, after their greeting. “There is nothing he can do to aid us,” Nick replied. “We shall set at work at once, and you must remain here with Mr. Strickland. Find out, Patsy, whether the photographer on the floor above has arrived. He promised to come down early this morning.” Patsy hastened from the parlor in which they had been received, while Nick and Chick at once proceeded to the rear rooms. “We’ll begin with the bathroom,” said Nick, leading the way. “Daylight may reveal more than I was able to discover last night. Ah, by Jove, I thought so.” He had entered the bathroom and raised the lower section of the small, ground-glass window. A glance at the stone sill outside, which he then began to inspect with a powerful lens, evoked his last more forcible remark. “It’s what I do not find,” Nick replied. “Notice the lack of dust on the upper surface of this stone. All that remains of the thin layer which ordinarily would be there is a small quantity next to each casing. The lens shows, too, that it has been rubbed in each direction, as if with a piece of cloth, or a garment.” “Plainly enough,” Chick agreed. “It would be indiscernible, nevertheless, except in a bright light.” “That was the difficulty last evening. We had not light enough.” “You now suspect----” “More than suspect,” Nick interrupted. “I now am convinced that one of the crooks, at least, entered through this window.” “But how could he have reached it? There certainly was no ladder used, or the janitor must have heard him. Nor is there any other window from which the rascal could have reached this one.” “If not from below, Chick, he must have come from above.” “From the photographer’s room?” “Or from the roof.” “Either would be possible,” Chick allowed. “But we discovered no evidence of it. Besides, Strickland stated that the bathroom door was locked, and Gordon found it so when they entered.” “That would have been no barrier to a crook clever enough to pull off a job of this kind. He would have pushed out the key and--stop a bit! We may find evidence of it.” Turning back, Nick removed the key from the bathroom door to examine it with his lens. He quickly found what he was seeking. “Here we have it,” he added. “The end projecting beyond the tongue has been gripped with a pair of nippers. Notice the marks they left on it. The rascal unlocked the door by turning the key with the nippers, relocking it by the same means before he left the flat.” “You think he went out through this window.”