[...] as he was talking the whore yawned, not because she wasn't interested in what he was saying but because she was tired, which irritated Sergio and made him say, in exasperation, that in Santa Teresa they were killing whores, so why not show a little professional solidarity, to which the whore replied that he was wrong, in the story as he had told it the women dying were factory workers, not whores. Workers, workers, she said. And then Sergio apologized, and, as if a lightbulb had gone on over his head, he glimpsed an aspect of the situation that until now he'd overlooked.
i dont actually remember if i know what the lightbulb refers to but i like this phrasing [how it invites the reader's curiosity, makes them want to puzzle out the answer - like in american gods when neil realises it's a two-man con]