plot thickens, the

plot thickens, the idiom
Circumstances are becoming very complex or mysterious. Today this term is often used ironically or half-humorously, as in His companion wasn't his wife or his partner—the plot thickens. Originally (1671) it described the plot of a play that was overly intricate, and by the late 1800s it was used for increasingly complex mysteries in detective stories.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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