He put down his cup. “You wish that?”
“I do.”
“You have seen what I have seen. Should not our ideas be the same?”
“I’m afraid you’re laughing at me,” I said stiffly. “Of course, I’ve no experience of matters of this kind.”
Poirot smiled at me indulgently.
“You are like the little child who wants to know the way the engine works. You wish to see the affair, not as the family doctor sees it, but with the eye of a detective who knows and cares for no one—to whom they are all strangers and all equally liable to suspicion.”
“You put it very well,” I said.
“So I give you then, a little lecture. The first thing is to get a clear history of what happened that evening—always bearing in mind that the person who speaks may be lying.”
I raised my eyebrows. “Rather a suspicious attitude.”
“But necessary—I assure you, necessary. Now first— Dr. Sheppard leaves the house at ten minutes to nine. How do I know that?”
“Because I told you so.”
“But you might not be speaking the truth—or the watch you went by might be wrong. But Parker also says that you left the house at ten minutes to nine. So we accept that statement and pass on. At nine o’clock you run into a man—and here we come to what we will call the Romance of the Mysterious Stranger—just outside the Park gates. How do I know that that is so?”