The doctor sat down heavily on the nearest chair. "I don't see--that it affects us," he protested feebly, "there is no offense in getting a tip about a failing property, is there, Sault?" "I don't know. Moropulos says it is conspiracy. They can prove it if--" "If--?" "If they find the letters which the manager wrote. Moropulos has them in his desk." Merville sprang up. "Then they must be destroyed!" he cried violently. "It is madness to keep them--I had no idea--of course he must burn them. Go back and tell him to do this, Sault." Ambrose Sault put his hand into the fold of his shabby jacket and brought out a bundle of documents. "They are here," he said in a matter of fact tone. "Moropulos says that you must keep them. They may get a warrant to search his house." "Keep them--I?" Merville almost screamed, "Moropulos is a fool--burn them!" Sault shook his head. "Steppe say 'no'. They may be useful later. You must keep them, doctor. It is Steppe's wish. Tomorrow I will start working on the safe." Dr. Merville took the papers from the outstretched hand and looked around helplessly. There was a steel box on his desk. He took out his key, looked again and more dubiously at the packet of letters and dropped them into the box. "What is this safe, Sault? I know that you are a devilish clever fellow with your hands and Moropulos mentioned something about a safe. You are not making it?" Sault nodded and there was a gleam in his fine eyes. "But why? Moropulos has a safe and Steppe must possess dozens. Why not buy another, if he must have a special place for these wretched things?" "You cannot buy the safe that I shall make," said the dark man quietly. "It has taken me a year to invent the dial--eh? Yes, combination. They are easy, but not this one. A word will open it, any other word, any other combination of letters, and there will be nothing to find." The doctor frowned. "You mean if any other person--the police for example, try to open the safe the contents are destroyed?" Sault nodded. "How?" The visitor, his business at an end, rose. "That is simple, a twist of the hand, unless the combination is true, releases a quart of acid, any of the corrosive acids will serve." Merville bent his head in thought. Presently he saw a flaw in the invention. "Suppose they don't touch the lock?" he asked. "Suppose they burn out the side of the safe--it can be done, I believe--what then?" Ambrose Sault gave that soft laugh of his. "The sides will be hollow, and filled from the inside of the safe, with water pumped in at a pressure. Cut through the safe, and the water escapes and releases a plunger that brings about the same result--the contents of the safe are destroyed." "You are a strange creature--the strangest I have met. I don't understand you," Merville shook his head. "I hope you will hurry with that safe." As Sault was at the door he asked: "Where did Moropulos find you, Sault?"