Can you solve the secret assassin society riddle? - Alex Rosenthal
Your agent is about to infiltrate a life or death poker game in a hidden back room of the grand casino. You’re on the trail of an elite society of assassins, each of whom carries a signature playing card corresponding to their role. You’ve received intel from a 100% reliable source about how they operate.
Their M.O. is to invite their victims to a high stakes game with one or more killers at the table. The game is a variant of poker played with a single, fair deck where every player receives two cards in secret. Each assassin immediately and covertly swaps one of the cards they’ve been fairly dealt with their signature card. Then the robo-dealer reveals three shared cards on the table.
After betting, the assassins play their signature cards as a signal that they’re ready. When the last one comes out, they go about their grim business. Today's game is no different, and your mission is to identify the assassins and save all the victims. Everyone at the table is either an assassin or a victim, and there must be at least one of each.
The game is about to begin when your agent finds the secret passage and talks her way into a seat at the table. Meanwhile, you’re monitoring the proceedings with an insect drone. If you can figure out who has swapped out a fairly dealt card with a new one, you can identify the assassins and alert your agent through her earpiece. The game begins.
Your drone doesn’t catch anyone’s sleight of hand, but it does manage to get a look at the cards each player holds. Suddenly — disaster. Someone swats the drone, breaking your video feed before the reveal of the shared cards. It goes into emergency mode and is just operational enough to send the following string of data about those three shared cards before shutting down for good.
And that’s it; you’ve lost your eyes and ears in the room. Your spy can’t see anyone else’s cards or tell you anything, so it’s up to you to figure this out, and fast. Who are the assassins? Pause here to figure it out yourself.
Answer in 3. Answer in 2. Answer in 1. You can start by combining the first two rules. The second tells us that there are at least two queens, and the first that there's at least one king. So we must have two queens and a king. The first rule then tells us that the king is either in the middle or the left. That’s all we can do for now, so let’s look at the suits.
By the same logic, we know that there must be two spades and one heart. And by the third rule, that heart must be in the middle or on the right. We can now make a table with our four possibilities. We can eliminate this one because it would require the deck having two queens of spades. We can’t rule out any other options, but we don’t actually need to; in every case, the three cards are the king of spades, the queen of hearts, and the queen of spades, in different orders.
And it just so happens that each of these players holds one of those cards. So, they’re the assassins, right? Well, hold on, there’s something odd. Player 2 and the agent both hold the same card. So, one of those must be a signature assassin card. But you know from your Intel that there’s at least one victim who is not the agent. How can that be?
Oh, no. There’s only one possibility: your spy is the assassin known as the king of diamonds, and she’s been playing you this whole time. The only victim is player 2. You rush in, grab hold of player 2 just before the bidding ends, and make a run for it. On your way out, you lock eyes with your backstabbing partner. You search her features, desperate for any sign of remorse or apology. All you get back is a poker face.