Or, the problem with pronouns.
You know pronouns — he, she, it, they, and all those other little words that get called up to fill in for common nouns (cat, dog, gerbil, pigeons) and proper nouns (Tom, Dorothy, Mount Rushmore, the Boston Red Sox) so that our sentences and paragraphs don’t get cluttered up with wall-to-wall names.
The thing about pronouns is that a pronoun is always going to be looking backward toward the noun that it’s standing in for — its antecedent (from a couple of Latinate building blocks meaning, roughly, “falling before”; a pronoun’s antecedent is the word that falls before it in the sentence.) And no matter what the actual intended antecedent for a particular pronoun may be ,the reader’s first impulse will be to associate it with the most recently occurring noun of the appropriate gender and number.
Most of the time, re-associating the pronoun with its proper antecedent only takes a fractional second of mental processing on the part of the reader. The thing is, though, all those fractional seconds start to add up, and the cumulative weight of all that extra time acts like a drag on your story’s forward momentum. Too much drag, and the reader’s going to get tired and give up.
Don’t let that happen. Watch your pronouns.