In 1939, as Poland falls under the shadow of the Nazis and the world goes to war, young Alma Belasco's parents send her overseas to live with an aunt and uncle in their opulent San Francisco mansion. There she meets Ichimei Fukuda, the son of the family's Japanese gardener, and between them a tender love blossoms, but following Pearl Harbor the two are cruelly pulled apart. Throughout their lifetimes, Alma and Ichimei reunite again and again, but theirs is a love they are forever forced to hide from the world.

Decades later, Alma is nearing the end of her long and eventful life. Irina Bazili, a care worker struggling to reconcile her own troubled past, meets the older woman and her grandson, Seth, at Lark House nursing home. As Irina and Seth forge a friendship, they become intrigued by a series of mysterious gifts and letters sent to Alma, and learn about Ichimei and this extraordinary secret passion that has endured for nearly seventy years.