It was by this time dark, and he could move into the upper part of the house with comparative safety. All day long the rain had been plashing into the area with a dismal sound; the dreariness of the weather and the dreariness of the house would have daunted any man who had not a serious purpose to sustain him. Frederick had held no further communication with the detective; during the day it was impracticable. But it had been arranged between them that when night came, the detective, if he had anything of importance to communicate, should drop a letter into the area, of course at such time and in such a way as should afford no chance of detection. Before going upstairs with his precious key, Frederick cautiously opened the door which led into the area, and saw that a small packet of brown paper had been dropped during the day. He picked it up and opened it; there was a stone inside, and round the stone a sheet of note paper, on which was written, in the detective's handwriting: "Mrs. H. has received to-day a large sum of money. Her friend, Mr. P., was with her for nearly two hours. Upon leaving her house he drove to the City and cashed a cheque for fifteen hundred pounds. He was in high spirits. There is something in the wind; it looks as if they are making preparations to flit. Mrs. H. is getting together as much ready money as she can lay her hands on. I have no doubt she and Mr. P. have arranged to-day to go away together. Nothing further to say on that head. Your young lady friend in No. 118, Becky, is quite safe, but she looks anxious. On your account, I guess. Her little friend, Fanny, is a brick. We shall be on the watch all night in the Square. If you are in want of help, use your whistle." Not being in want of help at present, Frederick destroyed the letter, and went upstairs to the first floor. Opening the door of the room his father had occupied, he saw that no person had entered it during the day; everything was as Pelham had left it early in the morning. Frederick, by the light of his lantern, looked around for drawer or desk. A chest of drawers was there, unlocked and empty; a desk also, which had been broken open, and which the key he had found would not fit. As he left the room he saw, lying in a corner of the wall, a large key. It was the key of his father's room. He put it in the lock, and it turned easily. "Pelham would be astonished to-night," he thought, "if, when he came, he found the door locked against him. But that would be putting him on his guard. I will open the trap for him instead of closing it. Murderer! Your hour is approaching!"