Galton Morrow is a man with a mission. An upstanding Progressive Era doctor and venereal disease expert, he’s intent on saving the fallen souls of Boston from the wages of their ignorance, hypocrisy, and sin. Galton is proud of the way he worked his way up into the best of Boston society—and the best of society wives—and considers his blood as good, if not better, than anyone’s: after all, he’s the product of a scientific breeding experiment conducted by utopian visionaries at the Oneida Colony in upstate New York, his parents ostensibly selected by community leaders for the outstanding quality of their bodies, minds, and spirits. The entire story is told through diary entries, beginning with Galton’s, and including those of three members of the colony. 

Galton’s world begins crumbling when an engaging young historian named Hope, another Oneida descendant, brings the diary of Galton’s father, Josiah, to his attention. While initially disgusted with Josiah’s backwoodsiness and lasciviousness, Galton becomes obsessed with the diaries (written in a code that requires considerable effort to decipher), which reveals what he has always secretly suspected: this man may not have been his biological father. His self-image shaken, Galton travels to Oneida and, with Hope’s help, eventually uncovers his real origins through diaries left by his mother and by the woman responsible for overseeing her childbearing. He discovers that while Josiah clearly loved his mother, the elders refused the match, attempting unsuccessfully to force separations between them while compelling his mother to procreate with others.