"_Someone_ is in there, but _where_?" said Marriott. Again he urged his friend to go in with him. But Greene refused point-blank; said he had been in once and had searched the room and there was nothing there. He would not go in again for a good deal. They shut the door and retired into the other room to talk it all over with many pipes. Greene questioned his friend very closely, but without illuminating result, since questions cannot alter facts. "The only thing that ought to have a proper, a logical, explanation is the pain in my arm," said Marriott, rubbing that member with an attempt at a smile. "It hurts so infernally and aches all the way up. I can't remember bruising it, though." "Let me examine it for you," said Greene. "I'm awfully good at bones in spite of the examiners' opinion to the contrary." It was a relief to play the fool a bit, and Marriott took his coat off and rolled up his sleeve. "By George, though, I'm bleeding!" he exclaimed. "Look here! What on earth's this?" On the forearm, quite close to the wrist, was a thin red line. There was a tiny drop of apparently fresh blood on it. Greene came over and looked closely at it for some minutes. Then he sat back in his chair, looking curiously at his friend's face. "You've scratched yourself without knowing it," he said presently. "There's no sign of a bruise. It must be something else that made the arm ache." Marriott sat very still, staring silently at his arm as though the solution of the whole mystery lay there actually written upon the skin. "What's the matter? I see nothing very strange about a scratch," said Greene, in an unconvincing sort of voice. "It was your cuff links probably. Last night in your excitement--" But Marriott, white to the very lips, was trying to speak. The sweat stood in great beads on his forehead. At last he leaned forward close to his friend's face. "Look," he said, in a low voice that shook a little. "Do you see that red mark? I mean _underneath_ what you call the scratch?" Greene admitted he saw something or other, and Marriott wiped the place clean with his handkerchief and told him to look again more closely. "Yes, I see," returned the other, lifting his head after a moment's careful inspection. "It looks like an old scar." "It _is_ an old scar," whispered Marriott, his lips trembling. "_Now_ it all comes back to me." "All what?" Greene fidgeted on his chair. He tried to laugh, but without success. His friend seemed bordering on collapse. "Hush! Be quiet, and--I'll tell you," he said. "_Field made that scar._" For a whole minute the two men looked each other full in the face without speaking. "Field made that scar!" repeated Marriott at length in a louder voice. "Field! You mean--last night?" "No, not last night. Years ago--at school, with his knife. And I made a scar in his arm with mine." Marriott was talking rapidly now. "We exchanged drops of blood in each other's cuts. He put a drop into my arm and I put one into his--"