The curator swore the rare sapphire was stolen between 2:00 PM and 3:00 PM while he was inside the locked vault. Three people entered the museum during that hour: the cleaner, who wiped the floors; the postman, who dropped off a heavy box; and the tour guide, who led a group outside. The cleaner left footprints leading in and out, the postman's signature is in the front logbook at 2:15, and the tour guide has mud on her shoes. Yet, the detective arrested the curator immediately. Why?
The curator was inside a locked vault.
A vault cannot be locked from the inside while someone is actively guarding or working within it, or more simply, if the curator claimed to be inside a locked vault during the theft, he trapped himself with the gem or fabricated his alibi since a locked vault prevents outside access.
About this riddle
Detective riddles are tiny mysteries. Look for the detail in the story that does not fit; it is usually the clue that solves the case.
Difficulty: Medium. More like this: Detective riddles with answers or try Truth & Lie Island for a different kind of puzzle.
More detective riddles
The antique dealer was found murdered behind his counter. A pocket watch was clutched in his stiffening hand, its hands permanently frozen at 4:15. The detective immediately knew the watch was a red herring planted by the killer. What proves the watch was faked?
The victim was found in a locked room with no signs of forced entry. On the desk sat a glass of water with a floating ice cube and a pool of spilled ink. Detective Marsh deduced the victim had died of natural causes hours before. How did the ice cube help him?
A jeweler reported a robbery. He claimed a masked thief smashed the display window from the outside at midnight. Detective Sterling examined the shattered glass shards and immediately charged the jeweler with insurance fraud. What did the glass reveal?
A security guard at a warehouse reported that a thief broke in, tied him to a chair, and stole a shipment of copper wire. When Detective Sterling arrived, he found the guard sitting upright, securely tied to a rolling office chair with his hands bound behind his back. The chair's wheels were unlocked, and the warehouse floor was completely smooth concrete. Sterling arrested the guard for insurance fraud. Why?
A banker was found dead in his locked office with a gunshot wound to the head and a revolver in his right hand. A suicide note rested on the desk. Detective Sterling examined the position of the revolver, the trajectory of the bullet, and the fact that the banker was strictly left-handed. He immediately called for a murder investigation. Why?
A jewel thief claimed he couldn't have robbed the penthouse because he was bedridden with a broken leg and his heavy plaster cast went all the way up to his hip. Detective Vega checked the suspect's apartment, looked at his bathroom sink, and immediately charged him with the crime. What did Vega see?