“One characteristic scruple detained you. You did not shrink from undoing God’s work by destroying the material body of the man you hated, but you trembled for the prospects of his soul if his life was thus suddenly brought to an end. You decided that you must warn him of the danger he ran, but how were you to warn him without risk of discovery? You sent him a present of a book about immortality; that seemed natural enough, as it was the subject he had been lecturing about. Then, anonymously, you sent him a message which consisted only of figures, yet so arranged that a clever man like Brotherhood could see that the figures were a cipher, and that this book was the key to the cipher. The message you sent ran, ‘You will perish if you go back upon your faith.’ Then you felt you had warned him sufficiently. As a matter of fact, he left the book in the train on Monday, and therefore your warning, which reached him on Tuesday, was in any case too late. “Your alibi was brilliantly thought out beforehand. You went up to London, being careful to tell us all that you were going. You took with you no weapon except a heavy stick. But you had a powerful ally in the grey fog which hung over the railway line that day; the fog which made the movements of the trains slow, their timing uncertain, their carriages almost invisible from each other. You had chosen your day well. You knew, I take it, beforehand that Brotherhood’s bankruptcy would soon be public property; you took good care, anyhow, to inform yourself of the fact when you got up to Town. That meant that the way was clear for you; the murder would be interpreted as suicide. “You went up by the same train as Brotherhood; you took care to come back by the same train. You shadowed him, I suppose—easy work for you to do that unseen in the grey fog. You saw him enter a carriage which was (I think) the last of a coach. That was probably a disappointment to you, because you could not take the one immediately behind. No matter, you took the one immediately in front instead. Each travelled first, and each was alone in his carriage; it was not difficult to secure that in such weather, on such an unfrequented train. The whistle blew, and you went out into the fog. “You could do nothing on the first stage of your journey; it was necessary for you to reach ground that you knew; you could not be certain, in the fog, that the blow would be fatal if you struck it elsewhere. You waited till the train got to the beginning of the Paston Oatvile viaduct, and there, as you expected, it was held up by the signals. That meant that you were just at the beginning of the viaduct, so that a body falling over must necessarily go to its destruction. It meant also, owing to the curve, that the other coaches were all but out of sight from yours; in any case, you were hardly visible in the fog.