Tom Carew, known with affection as “the mad Irishman,” was a British special operations officer during World War II. Specifically, he was a Jedburgh, one of 300 officers dropped behind enemy lines to train guerrilla fighters. To understand his military history required archival deep-diving, while plumbing the (relatively) peaceful years involved sifting through diaries and letters, sorting out generations of mismatched marriages (temperament, class), and engaging in capacious acts of empathy and imagination. At one point, her father survived by clinging to a rafter of a hut; had the Japanese soldier searching for him looked up instead of helping himself to the rice in a pot, Tom Carew would have been killed and any possibility of Keggie and her siblings extinguished: “The fine splinter of time between existing and not existing.” Postwar, the mad Irishman wrestled with debt and burned through marriages — first to the mysterious Margo; then to Keggie’s mother, Jane, who worked in codes and ciphers during the war, and whose rage became clinically toxic. Incapable of solving a problem in a conventional manner, Tom Carew drilled a hole through the floor of his car, enabling him to pee through a siphon — onto the road, he thought — until the ferocious stench required investigation. Keggie, flaunting convention herself, took off for Barcelona at seventeen, then knocked around the U.S.