"Acres of Diamonds," the third episode of season four of HBO's Boardwalk Empire, airs tonight at 9. As the story progresses, certain details and figures of American history will populate the story. Instead of blissfully nodding your head and putting foolish trust in your faint memory of ninth-grade history, get prepared with our spoiler-free precap. Hell, it might even elevate the experience for you.

It's a good feeling to be in the know.

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