Ava and Joseph Simon reluctantly put their 9-year-old son, Henry, and four-year-old daughter, Catherine, in the care of their son's teacher, who will escort them on a boat to mainland England. Just as the ferry is about to leave, the teacher's sister, Lily appears. The two trade places: Helen doesn't want to leave Guernsey, and Lily is desperate for a fresh start. Lily is the one who accompanies the children to England, and Lily is the one who lets Henry get on a train by himself, deciding in a split second to take Catherine with her and walk the other way. That split-second decision lingers long after the war ends, impacting the rest of their lives. Perfect for readers of , is at once heartbreaking, thought-provoking, and uplifting.