I watched both men take a sip, and saw them set down their glasses with a thoroughly satisfied air. Then the man with the scar made a sudden remark to the other, who, turning his head, looked away over his shoulder into the restaurant. His attention could only have been withdrawn from the table for a couple of seconds at the most, but in that fraction of time something happened which set my heart beating rapidly in a kind of cold and tense excitement. So swiftly, that if I had not been looking straight in the mirror I should have missed seeing it, the man with the scar brought his hand down over his companion's glass. Unless my eyes were playing me a trick, I distinctly saw him empty something into the wine. There are rare occasions in life when one acts instinctively in the right way before one's mind has had time to reason matters out. It was so with me now. Without stopping to think, I whipped out a pencil from my pocket, and snatched away a piece of white paper from underneath the small dish of candied fruit in front of me. Spreading it out on the table I hastily scribbled the following words: "Don't drink your wine. The man with you has just put something into it." I folded this up, and beckoned to one of the waiters who was standing by the door. He came forward at once. "Do you want to earn half a sovereign?" I asked. "Yes, sir," he answered, without the faintest air of surprise. "Listen to me, then," I said, "and whatever you do don't look round. In the farther corner behind us there's a gentleman with an eyeglass dining with another man. Go up the centre of the room and give him this note. If he asks you who it's from, say some one handed it you in the hall and told you to deliver it. Then go and get my bill and bring it me here." The waiter bowed, and taking the note departed on his errand, as casually as though I had instructed him to fetch me a liqueur. All the time I had been speaking I had kept a watchful eye on the mirror, and as far as I could tell neither of the two men had noticed our conversation. They were talking and laughing, the man I had sent the message to lightly fingering the stem of his wine-glass, and blowing thin spirals of cigarette smoke into the air. Even as I looked he raised the glass, and for one harrowing second I thought I was too late. Then, like a messenger from the gods, the waiter suddenly appeared from behind one of the pillars and handed him my note on a small silver tray. He took it casually with his left hand; at the same time setting down his wine-glass on the table. I saw him make an excuse to his host, and then open it and read it. I don't know exactly what I had expected him to do next, but the result was certainly surprising. Instead of showing any amazement or even questioning the waiter, he made some laughing remark to his companion, and putting his hand in his pocket pulled out a small leather case from which he extracted a card.