Blackfile №3: The Long Exposure at Harrowfell

How to start

1. Open it in your AI. Tap Open in ChatGPT or Open in Claude, and press send, or paste the play prompt into any assistant that can open links. No paid plan required.
2. The game loads. The case file carries the sealed hash and opens the observatory at a quarter past midnight.
3. Investigate. Twenty moves across six places, six suspects, and a station that kept its own records.
4. Accuse and verify. Name the killer and the hour, then open the seal and rebuild its hash at aigamecards.com/verify.

Questions

How do you stop the AI from deciding the murderer at the end?

Kite's killer, the hour of the killing, the method and the reason were written out and hashed with SHA-256 before the card shipped, and that commitment is printed in the case file you paste. The game master runs the fixed text and cannot decide the guilty party is whoever you happen to suspect at move fifteen. When you accuse, it grades you from the card first, prints your result, and only then opens the sealed reveal and hands you its address. Paste that reveal into the verifier at aigamecards.com/verify and the published commitment rebuilds in front of you.

Is the case actually solvable, or is it guesswork?

It is solvable by deduction. Every clue the answer rests on is keyed to a place or a person you can reach inside the twenty moves, each innocent is cleared on independent grounds, and nothing is settled by a roll or a leap. The station kept records of its own, and what they say is as much evidence as anything the six tell you.

What are the twenty moves, and can I run out?

One examination, one search or one visit to one person costs one move, and a visit costs that one move however many questions you ask — though what a person hides you still have to press out of them. Walking between places, reviewing the timeline and saving are free. Sixteen clues are keyed across six places and six people, so a thorough night leaves you a little slack and a wandering one does not — the wrong object costs exactly what the right one costs. At move twenty the constable is at the door, and you may still make your one accusation before he takes the file. Decline, and the case leaves your hands with whatever you found.

Do I need dice, an account or any tools?

No dice and no randomness — this case turns on records and objects — and no account beyond the chat app you already use. Paste the case file into ChatGPT, Claude or Gemini and Harrowfell opens at a quarter past midnight with Kite still under a sheet in the dome lobby. Say "save" at any point to print a save code, then paste it into a fresh chat with the case file to resume on the same move. Checking the seal afterwards wants nothing but the verifier at aigamecards.com/verify: pick the game, paste the reveal the card hands you, and the published SHA-256 rebuilds.

How is this different from Blackfile №1 and №2?

Different decade, different kind of place, different shape of proof. №1 is a 1925 country house and a disappearance from a bolted glass conservatory. №2 is a 1929 snowbound spa hotel and a death over a nightcap. №3 is a working scientific station on a Northumberland fell in 1953, where the instruments keep their own account of the night. Play them in any order; they share nothing but the seal.