"I picked his pocket to make matters even, and substituted my knife similarly wrapped up. "When we got to this house he gave the knife to Annie O'Neil, who put it on Miss Stevens' pillow when she went upstairs to call Mrs. Stevens." "You have not explained the robberies at my house," said Colonel Richmond. "I'll do that over there. Is the rest of it clear? Has anybody a question to ask?" Nobody spoke. "Annie O'Neil," said Nick, "I'll leave here in Patsy's charge. Horace Richmond, come with us." Horace looked ugly for a moment, and then he calmed down and sullenly complied with Nick's order. Judge Lorrimer begged to be of the party in order to see the explanation of the mysterious robberies of which he had heard. Two hours later they all stood in Mrs. Pond's room. "The essential part of this matter," said Nick, "was this door which appeared to open and close of itself. "I saw that at a glance, and made a secret investigation. It is done by electricity. "There's a magnet in the casing which is powerful enough to swing the door to, after which the same magnet pushes this little bolt--which looks like an ordinary screw--into position, and that holds the door, but not very steadily. "You may say that this should have given me the criminal at once, but it didn't. "You see, this electro-magnet works whenever a current is turned into the wires. Horace was clever enough to have the wires lead all over the house. "A connection with the electric light wires, furnishing the current, can be made in almost every room in the house. "Of course, I suspected Horace at once, because his room was directly overhead. In fact, the two are connected, as you see, by a ventilator in the form of a pipe with a grated opening in each room. "The grating here, you see, is open." "But, bless me," exclaimed Judge Lorrimer, "no thief could come through such a place. Why, it isn't six inches square." "Step in here a minute and see," said Nick, and then he called out: "All ready, Chick!" The whole party had by this time gone into Mrs. Pond's sitting-room. Nick said hush, and pointed to the ventilator. Most of the party could see it through the door. Instantly there appeared a mass of green feathers, and then Horace Richmond's parrot fluttered noiselessly down into the room. For a minute or two it ran around the floor. Then it flew up on to the dressing-table, seized a small gold bar pin in its beak, and flew back into the ventilator pipe. "A nice trick," said the detective. "I believe it took you some time to teach the bird that." "About a year," growled Horace. "The bird was well trained before." "Is it all clear?" said Nick. "Perfectly," said the colonel. "But how did you get at it?" "Simply enough. There was only one way into this room when those robberies were committed, and the parrot was the only living thing in the house that was small enough to go through that pipe and intelligent enough to do the trick.