The call came at three in the morning. When don’t they? A collector’s prized first edition of The Maltese Falcon had vanished from a climate-controlled safe room. The door was still locked from the inside. The window hadn’t been opened in years.

I’ve learned that impossible crimes usually have very possible explanations. Someone had a key. Someone knew the code. The question was always who—and why.

By dawn, I’d ruled out the butler. He was in Argentina. The real culprit turned out to be considerably more mundane: a humidity sensor gone bad, a panic-stricken conservator, and a manuscript hastily relocated to “safety” in the basement. Case closed. The book was returned. The collector offered me a cigar. I declined—I don’t smoke.

Lessons learned: Always check the maintenance logs. And never trust a locked room. Locks keep honest people honest. That’s about it.