You gave too much rein to your imagination. Imagination is a good servant, and a bad master. The simplest explanation is always the most likely.
 Agatha Christie, The Mysterious Affair at Styles (1920). copy citation

Context

“Events proved that I was right in my supposition.»
«That was very ingenious,» I could not help admitting. «I must confess that the conclusions I drew from those few scribbled words were quite erroneous.»
He smiled.
«You gave too much rein to your imagination. Imagination is a good servant, and a bad master. The simplest explanation is always the most likely.»
«Another point—how did you know that the key of the despatch-case had been lost?»
«I did not know it. It was a guess that turned out to be correct. You observed that it had a piece of twisted wire through the handle.” source

Meaning and analysis

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