I couldn't get that to work at all and was about to give up and then realized you didn't use the curly smart quotes. Once I changed it to smart quotes, it would work somewhat, but it will also pick up any sentence or paragraph that doesn't immediately start with a quote. So it would pick up paragraphs like this:
Pamela shuddered. “We’ve been making ourselves polite to a murderess.”
And there's usually far too many of those types of sentences to want to read through over 500 of them to find the beginning quote buried further in.