system
Given the following post, respond as if you're commenting on Reddit:
human
[Sherlock Holmes: A Study in Pink] "It's not chance, Mr. Holmes, it's chess." - but what were the moves?

The villain in the Sherlock Holmes BBC episode *A Study in Pink* claims that his murders aren't due to luck, that he's presenting his victims with a puzzle that each fail to solve. Could someone explain the puzzle involved? Was it just some form of psychological manipulation, or was the murderer not as smart as he thought he was and just lucky that many times in a row?
gpt
Let's go over it.

Psycho with a gun sits you down, presents two identical vials- one with poison, one without. You take one, he takes the other, and you get to choose.

He slides one across the table and says to pick.

A certain kind of person is numb with shock and almost paralyzed- it's well known that once somebody believes they are about to die they become very passive. Such a person will automatically take the vial in front of them.

But you- you are active, and you figure that he shoved the poison to you in the expectation you'd take it. You grab the poison in front of him instead and then lock eyes, watching him like a hawk.

He's calm. Smiling a little, even. Just a happy, silly little man with no real cares.

Shit. Um. Either he knows you just grabbed the poison, which means that smile is because he's about to win, or he knows it isn't poison and is bluffing you.

But if you just grabbed the poison, why would he telegraph it by smiling? He should have put on a poker face. So it must be the good pill you have.

You test the theory, you shove the pill back in front of him and choose the pill closest to you instead. Now the smile is gone and the stone face is back.

You cracked the code. When he's smiling, he hates your choice and is trying to bluff you. When he has a poker face, he likes your choice.

You grab the pill in front of him.

One, two, three, and you both take your medicine. And you die.

He knew how you would think, whether you were passive or active, how many layers you'd unpeel before being satisfied you'd found them all. It's not chance, it's chess. Only there's only one move before checkmate. His move is to suss out what kind of person you are before deciding which pill to place in front of you. Your move is to suss out his decision making process before choosing.

The only possible solution is to make it truly random- seize both vials, mix the pills, then grab one without thinking. Coin toss beats playing chess with Kasparov.