A 2021 Scott O'Dell Award Winner A Society of Midland Authors Winner in Children's Fiction A Bank Street Best Book of the Year 2021 A novel in verse about a young deaf boy during World War II, the sister who loves him, and the conscientious objector who helps him. Inspired by true events. Henry has been deaf from an early age--he is intelligent and aware of langauge, but by age six, he has decided it's not safe to speak to strangers. When the time comes for him to start school, he is labeled "unteachable." Because his family has very little money, his parents and older sister, Molly, feel powerless to help him. Henry is sent to Riverview, a bleak institution where he is misunderstood, underestimated, and harshly treated. Victor, a conscientious objector to World War II, is part of a Civilian Public Service program offered as an alternative to the draft. In 1942, he arrives at Riverview to serve as an attendant and quickly sees that Henry is far from unteachable--he is brave, clever, and sometimes mischievous. In Victor's care, Henry begins to see how things can change for the better. Heartbreaking and ultimately hopeful, Helen Frost's All He Knew is inspired by true events and provides sharp insight into a little-known element of history.