Very well done episode and I applaud Sir Alfred for his innovation in this. Without spoiling it, let's just say that the end result was probably very taboo in his day while not surprising for today's standard. When you watch this, be sure to keep in mind that this was a first for them. Everyone has tried to copy Hitchcock's surprises but none have ever mastered it as he did.
I only have one thing that bothered me. I found it odd that someone plays poker, evidently on a regular basis, with someone and was not aware that he was engaged to a woman in the past. Perhaps they were newly acquainted, but it didn't appear to be that way. That's a minor nit-pick, but a head scratcher in any case.