As soon as he locked the door of his sanctum, he proceeded to change his clothing. In a quarter of an hour he had changed his appearance so completely that his most intimate acquaintance could not have recognized him. What did he intend to do? From the manner in which he acted, it was quite clear that he did not propose to remain in. He examined his notebook before leaving the room, and as he went out he muttered: “We will see what kind of place Miss Porter lives in.” CHAPTER VI. THE THREAT. Carter desired to learn something about Isabella Porter. Her appearance at this time and her anxiety to secure the papers which had been left in Mr. Wright’s possession so many years before seemed peculiar. As the detective reviewed the incidents, and recalled the record of Peters’ death to his mind, he was almost certain that the man had been attacked by some one who desired to put him out of the way. Was Peters’ death planned because he had in his possession these damaging papers? Carter pondered over this question. The circumstance was puzzling. Why was no attempt ever made until now to get possession of the documents? How did Isabella Porter come to know or suppose that they were in the possession of Mr. Wright? Was it any wonder that Carter was in a quandary when these questions were presented to his mind? He did not know what to think. He was in the dark. There was a veil before his eyes, figuratively speaking. He felt that Isabella Porter had some connection with the mystery of the Red Dragon Inn, but what this connection was he could not determine. Presently he arrived at the address on West Nineteenth Street. It was an apartment house. He went into the vestibule and examined the names on the letter boxes. The name of the woman was not among them. “It is as I supposed,” the detective muttered, “she does not live here, and she gave Mr. Wright this address simply as a blind.” To make sure that he was not wrong in his surmise, Carter called on the janitor and questioned him. The man did not know any woman by the name of Isabella Porter, and he was sure that no woman answering to her description lived in the house. “She had some deep object in view when she gave that false address,” the detective thought. “The discovery alone is sufficient to make one suspect her.” Early the next morning the detective called at the address on Fifth Avenue which he had found in the record of Peters’ death. No one knew anything about any person by the name of Porter. He returned to the hotel, and went to Mr. Wright’s room, intending to remain there until the woman called. He sent a message to the cashier of the safe deposit company, stating that he had important business on hand, and he would see him later in the day. Noon arrived, and Isabella Porter did not appear. Carter was impatient. “I’ve wasted the whole morning,” he remarked to Wright.