plot device

A plot device is an element introduced to a story to affect or advance the plot. In the hands of a skilled writer, the reader or viewer will not notice that the device is a construction of the author—it will seem to follow naturally from the setting or characters in the story. A poorly-written story, on the other hand, may have such awkward or contrived plot devices that the reader has serious trouble maintaining  suspension of disbelief; indeed, the devices may even leave plot holes.
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