"How?" demanded the colonel. "You forget the man was in a car. He must have heard another car had there been one."
"I should imagine that he not only heard it, but also saw it," said Amberley. "Though I incline to the belief that the murderer was on a motor bicycle."
"Oh, you do, do you? And why?"
"Merely because if you are right in assuming that he lay in wait for Dawson a motor bicycle could have been hidden in the hedge, or possibly run into the field behind. There was a gate. But you may have your car if you like. The main point is that the murderer shot Dawson either from a place of concealment (which probably means that the actual place of meeting was known to him), or from some vehicle driven towards Dawson's car."
The colonel thought it over. "Yes. Quite possible, but not conclusive, Amberley. Not conclusive, you know. Say that I concede it for the purposes of discussion. With whom was the assignation made?"
"I suggest, Colonel, that you depute my friend Fraser to find that out. He won't succeed, of course, but it will keep him occupied for a bit."
"Really, really, Amberley!" expostulated the colonel half-heartedly. "If you haven't any theories to fit that, then tell me what you suppose the motive to be that prompted the murderer to stop the meeting at all costs? Or can't you advance an opinion on that either?"
"Oh, I can tell you that," replied Amberley. The motive was robbery, of course."
"Robbery? My dear fellow, what are you talking about? A moment ago you refused to listen to that theory!"
"Oh, no, I didn't," said Amberley calmly. "I only begged you to rid your mind of the bandit notion. I see you haven't succeeded. I wish you'd try. It's beginning to bore me."