When the killer’s identity is revealed at the end of a murder mystery, you are totally floored because you never saw it coming.

In disbelief, you riffle through the pages to revisit the earlier parts of the story. And only then do you begin to see how cleverly the author has employed misdirection and all sorts of other tricks to confound you.

That’s what makes whodunits so irresistible.

There are infinite plot patterns that lead to “unexpected perpetrators,” but there is one example in particular that I must mention here.

In it, the iconic Belgian detective Hercule Poirot uses his........

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