She was an immaculate housekeeper and a good cook who kept within the budget Leo allowed for groceries. But their house on the road to Saltwater State Park in Des Moines wasn’t homey. The wood floors were dark; Leo liked the brown furniture, his trophies of dead animals mounted on the walls, and his cabinets filled with guns.

Both Leo and Sarah lived behind masks, trying to keep their secrets from prying eyes. He wanted his friends and other people to view him as a good family man. Like his own parents’ scrapbook, where he and his brother Ken smiled for the camera, the younger Garcia’ album is full of...