Leonard Darwin had a lot to live up to. He was the son of the legendary Charles, and several siblings proved to be brilliant scientists as well. But Leonard never quite measured up as a mediocre military officer and two-bit politician. In his fifties, he pronounced his life a “failure.” But in his sixties, he finally found his calling—the dark pseudoscience of eugenics, a field he embraced in part to prove that he wasn’t the failure he imagined.