Answer:
I'm pretty sure the punctuation error is in the third sentence;
'This struggle plays out chiefly through the protagonist; Charlie, who anchors the film brilliantly.'
Just after the word 'protagonist', the author uses a semi-colon (;). A semi-colon is used to link two separate clauses that have similar ideas together. It turns two clauses into one.
In this situation, the semi-colon is not doing that, because that would imply that if we were to separate the "two clauses", it would look like this:
"This struggle plays out chiefly through the protagonist. Charlie, who anchors the film brilliantly."
This wouldn't make sense. Instead of a semi-colon, the author should've used a comma!