One day, the police receive an anonymous tip that a robbery is about to occur on the fortieth story of a tall building. They grab a car and drive as fast as they can to the site. On arrival, they quickly cordon off the building and rush to the fortieth floor on the elevator. However, upon arrival, they find nothing amiss. To be safe, they disguise themselves and surreptitiously stick around for an extra two hours but eventually return back to the station. However the next day, the police receive a call from a frantic man who had returned from a trip to find his flat ransacked and a taunting letter from the alleged thief. The police are left perplexed--how had the thief avoided detection?

edit for more information: The robbery occurred during the middle of the day. The information given in the tip is accurate. The frantic man who called the next day had indeed been robbed by the thief. He was the only person who's room had been robbed that day.

  • 2
    $\begingroup$ And did the man whose flat was ransacked live on the 40th story of the building the police went to? Is there any info about when the robbery happened? $\endgroup$
    – Dr Xorile
    Jan 5, 2019 at 2:26

2 Answers 2


The tip was accurate but

the police used the elevator and pressed the 40 button. Many buildings skip 13. Meanwhile the robbery occurred on the 40th story, which is numbered 41.


The fortieth floor is

Different based on the counting system used. British/Commonwealth countries consider the lowest floor (i.e. one not raised) as the ground floor, the one above as the first floor, and so on. The US and some other countries count the lowest floor as the first.

It is possible that:

The tipster was referring to one counting system, and the police another.


The robbery occurred on the floor above/below the floor the police went to. The thief ransacked the flat, and waited until the police returned to the station (removing the cordon around the building) before making off with his haul.

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    $\begingroup$ Equally plausible and good as the solution I accepted, but I happened to have that one in mind. $\endgroup$
    – 1848
    Jan 6, 2019 at 5:17

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