"Yes, and every other night, too. Haven't I just told you so? Directly we strike the viaduct I come to my feet by instinct."
"Always look out the same side, I suppose?"
"Yes, on the left. That's the platform side, you understand."
"Then if anybody had left the train there——"
"Anybody left the train! Why we were traveling at fifty miles an hour when we reached the viaduct. Oh, yes, if anybody had left the train I should have been bound to see them, of course."
"But you can't see out of both windows at once."
"Nobody could leave the train by the other side. The stone parapet of the viaduct almost touches the footboard, and there's a drop of ninety feet below that. Of course I see what you are driving at, Mr. Merrick. Now look here. I locked Mr. Skidmore in the carriage myself, and I can prove that nobody got in before we left London. That would have been too dangerous a game so long as the train was passing any number of brilliantly lighted stations, and by the time we got into the open we were going at sixty miles an hour. That speed never slackened till we were just outside Lydmouth, and I was watching at the moment that our pace dropped. I had my head out of the window of my van till we pulled up by the platform. I am prepared to swear to all this if you like. Lord knows how the thing was done, and I don't suppose anybody else ever will."
"You are mistaken there," said Merrick drily. "Now, what puzzles you, of course, is the manner in which the murderer left the train."
"Well, isn't that the whole mystery?"
"Not to me. That's the part I really do know. Not that I can take any great credit to myself, because luck helped me. It was, perhaps, the most amazing piece of luck I have ever had. It was my duty, of course, to take no chances, and I didn't. But we'll come to that presently. Let it suffice for the moment that I know how the murderer left the train. What puzzles me is to know how he got on it. We can dismiss every other passenger in the train, and we need not look for an accomplice. There were accomplices, of course, but they were not on the express. Why didn't Mr. Skidmore travel in one of the corridor coaches?"