"He was willing that Mannion should keep the money he had stolen; he might have schooled himself to stand the loss of the letters without attempting legal reprisal, but the innate integrity of the man precluded any idea of payment for the return of the letters. Mannion, let us suppose, counting upon making a fat thing out of the letters, asked the appointment by the river, upon the representation that he would return them. He knew that he could not induce Playfair to meet him in any other way. Playfair kept the appointment, but, instead of receiving the letters as a free act of restitution, was confronted with the demand for money as a condition of the surrender. Now, knowing James Playfair, as you did, Mr. Feversham, what in your opinion would he have said and done, when the real object of the night appointment was made known to him?" "He would have given Arthur Mannion a piece of his mind and he would have followed it up by a positive, indignant refusal to pay one cent for the letters." "Precisely," said Nick, with a smile of approval, "and that, according to my theory, is what Playfair did. What followed? The usual thing, when an honest, virtuously resentful citizen is brought face to face with a discomfited, murderous-minded villain. With bitter, ungovernable rage in his heart, Mannion sprang at Playfair's throat. And he had assistance. Alone he would have had difficulty in overcoming such a man of science and muscle as James Playfair was. The Russian friend of his was close at hand. Attacked suddenly by two powerful men, Playfair was overcome. It may prove to be the fact that no other motive than revenge for Playfair's refusal to be held up influenced the murderer when he made his attack, and it may turn out that the motive was a mixed one, in which revenge cut the smallest figure. The case is just opening, and it is not the time to adopt any hold-fast theory?" "Never mind the motive, Mr. Carter," said Feversham, almost fiercely. "We feel sure that Arthur Mannion is the assassin. Let us catch him and we can figure on motives afterward." "Do you think it would be advisable to arrest Mannion now?" There was an odd ring in the detective's voice. Feversham gave him a sharp look, and then impatiently replied: "Of course, I think it would be good policy. Don't you?" "No. I would like to locate him, to keep him under surveillance until the time is ripe to strike; but to arrest him now might prove to be a serious mistake. We haven't evidence enough to hold him, and his first act would be to sue out a writ of habeas corpus. If he regained his liberty through the writ, as he probably would, he might do one of two things--defy us, or skip the country." Feversham's hopes instantly fell to zero. He looked as if he had received a blow in the face. "Then we have nothing really to go upon," he said, in an acutely disappointed tone.