The new art of photography and the new science of embalming the dead came into standard practice in 1840-50s America. On the autism spectrum, Osborn Roche is a well-respected postmortem and battlefield photographer during the civil war. He and his nephew Ray travel with the Union army photographing battlefields and creating portraits for the soldiers. When Osborn meets Lou, a young woman dressed as a man to work as an embalmer for the Union, he is drawn to her beautiful, flickering irises, a condition known as Nystagmus and also a condition Osborn's mother had. He sees that Lou is also on the autism spectrum, and they quickly become friends. Lou works with her father, Henry Cattell, an actual historical person famous for embalming President Lincoln's son, Willy. Common for the time, Henry believes his daughter, Lou, should never marry or have children due to her condition. When he thinks Lou's friendship with Osborn may blossom into courtship, Henry threatens Osborn and takes Lou away. Having never had a friend before, Osborn is broken without Lou but goes on with Ray back to the Union army. Osborn accidentally finds himself in the middle of a major battle but manages to take remarkable photographs that make him a very famous photographer. When he and Ray attend his war photography book signing, Lou shows up in line with her uncle, Ben. Ben explains that Henry would have Lou sterilized by a surgical procedure. Ben suggests Lou go with Osborn, and she does. Osborn, Lou, his nephew, Ray, find a runaway slave named Abigail. All four head back to their home in Pittsburgh, pursued by the Union army. Along the way, Osborn and Lou decide to marry to thwart Henry's claim. Henry convinces the authorities that Lou's condition is insanity and that she has no idea what she's doing. Lou and Osborn must escape again, but this time to Indian territory, a place they should never be found.