Blackfile №3: The Long Exposure at Harrowfell

How to start

1. Open your AI. Start a new chat in ChatGPT, Claude, or Gemini. No paid plan required.
2. Paste the case file. It 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, and the shape of the proof is unusual: everyone is answering for the wrong minute, and only one of the six fails when you move it. A photographic plate that lay open in the telescope from 9:31 to 11:01 caught the blow and a wedge of white light, and a recording ammeter in the plant hut dates them to three minutes at 9:52 — ninety minutes before the death everyone swears to. What you find at 9:52 is not an empty chair. All six are accounted for — by cocoa, by a wash pump, by a hunting governor, by a lamp burning in a room whose measuring engine drew no current at all. One of those accounts is made of glass that was still wet in the darkroom, and finding which is the game.

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, solved by finding the one way out. №2 is a 1929 snowbound spa hotel and a poisoning, solved by clearing five people from the one cup. №3 is a working scientific station on a Northumberland fell in 1953, and it is solved by catching the station's own instruments recording a night that contradicts every person in it. Play them in any order; they share nothing but the seal.