Curious Tales / Episode 03
The Fail-Safe Room
A vault is found open without anyone touching its door. Follow the maintenance record and the fictional safeguards to explain what happened.
Watch. Pause. Make your deduction.The answer starts at 02:22. Pause before then if you want more thinking time.
Changing format pauses the film and keeps your place.
Full captions are included in the picture. English captions and a transcript are also available.
Original fictional mystery made with AI-assisted imagery, cinematic footage and narration; original synthesized score.
Read the full transcript — includes the answer
Spoilers follow. For the mystery first, watch the film above.
[00:00:00] [Printed Secret intro.]
[00:00:03] Two locks. An independent alarm. Yet the vault opened without a key, without a hand on the door, and without a sound.
[00:00:11] The morning checks had passed. That evening, the caretaker found the vault standing open. The maintenance record tells a different story from the final indicators.
[00:00:20] Here are the fictional vault’s exact rules. The magnetic catch holds only with mains power and an already closed door. It cannot pull an open door shut.
[00:00:32] When power fails, a gravity bolt drops to lock. A service pin can hold that bolt raised. A spring pulls the door open whenever neither lock holds.
[00:00:46] The independent alarm sounds on opening only if its battery is connected at that moment. Initially, the door is closed, power is on, and the battery is connected.
[00:01:00] At six oh one, a service pin is inserted. At six oh five, the alarm battery is removed for testing. The magnetic catch still holds the closed door.
[00:01:14] At six ten, the mains power fails. At six eleven, it returns. Those are the only changes during that minute.
[00:01:28] At six twelve, the service pin is removed. At six fourteen, the battery is reconnected. At six sixteen, the caretaker finds the door open.
[00:01:42] When could the vault have opened by itself? Why was there no alarm? And why did restoring everything fail to close it?
[00:01:54] The records are complete. Nobody used a key or moved the door. There is no extra failure. Compare the operating rules with the order of events.
[00:02:08] [Thinking pause. Answer follows; pause here to solve.]
[00:02:22] The door opens at six ten, when the power fails. The magnetic catch releases. The service pin prevents the gravity bolt from dropping. Neither lock holds.
[00:02:34] The spring opens the door, and the disconnected battery leaves the alarm silent. When power returns, the magnet cannot catch a door that is already open.
[00:02:45] The safeguards worked separately in the morning. Their temporary failures overlapped that evening. Restoring the controls did not restore the door’s position.
[00:02:54] Another mystery awaits at The Printed Secret. What would you check first?