At least he could satisfy his mind upon one point. CHAPTER XV A LETTER IN THE GRATE Grimm's Hotel is in reality a block of flats, with a restaurant attached. The restaurant is little more than a kitchen from whence meals are served to residents in their rooms. Frank's suite was on the third floor, and Mr. Mann, paying his cabman, hurried into the hall, stepped into the automatic lift, pressed the button, and was deposited at Frank's door. He knocked with a sickening sense of apprehension that there would be no answer. To his delight and amazement, he heard Frank's firm step in the tiny hall of his flat, and the door was opened. Frank was in the act of dressing for dinner. "Come in, S. A. M.," he said cheerily, "and tell me all the news." He led the way back to his room and resumed the delicate task of tying his dress bow. "How long have you been here?" asked Mr. Mann. Frank looked at him inquiringly. "How long have I been here?" he repeated. "I cannot tell you the exact time, but I have been here since a short while after lunch." Mr. Mann was bewildered and still unconvinced. "What clothes did you take off?" It was Frank's turn to look amazed and bewildered. "Clothes?" he repeated. "What are you driving at, my dear chap?" "What suit were you wearing to-day?" persisted Saul Arthur Mann. Frank disappeared into his dressing room and came out with a tumbled bundle which he dropped on a chair. It was the blue suit which he usually affected. "Now what is the joke?" "It is no joke," said the other. "I could have sworn that I saw you less than half an hour ago in Camden Town." "I won't pretend that I don't know where Camden Town is," smiled Frank, "but I have not visited that interesting locality for many years." Saul Arthur Mann was silent. It was obvious to him that whoever was the occupant of 69 Flowerton Road, it was not Frank Merrill. Frank listened to the narrative with interest. "You were probably mistaken; the light played you a trick, I expect," he said. But Mr. Mann was emphatic. "I could have taken an oath in a court that it was you," he said. Frank stared out of the window. "How very curious!" he mused. "I suppose I cannot very well prosecute a man for looking like me--poor girl!" "Of whom are you thinking?" asked the other. "I was thinking of the unfortunate woman," answered Frank. "What brutes there are in the world!" "You gave me a terrible fright," admitted his friend. Frank's laugh was loud and hearty. "I suppose you saw me figuring in a court, charged with common assault," he said. "I saw more than that," said the other gravely, "and I see more than that now. Suppose you have a double, and suppose that double is working in collusion with your enemies." Frank shook his head wearily. "My dear friend," he said, with a little smile, "I am tired of supposing things. Come and dine with me." But Mr. Mann had another engagement. Moreover, he wanted to think things out.