The curator found the rare diamond missing from its pedestal, replaced by a cheap glass marble. The gallery was locked from the inside with no signs of forced entry. The security guard swore he never left his desk near the north exit, and the only other person inside was the night cleaner, who was mopping the south gallery. Yet, the detective immediately arrested the guard. Why?
The security guard's desk was near the north exit, but the cleaner was in the south gallery. However, the diamond was stolen from the east wing. Wait—actually, the guard claimed he never left his desk, but the glass marble was warm to the touch, and the guard's coffee mug was ice cold.
A glass marble absorbs body heat quickly when held. The guard claimed he never touched the display, but holding the replacement marble in his hand to swap it left it warm.
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.
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