Noriko Oi, a Japanese-Canadian woman who has been living in Montreal for more than 20 years, is about to return to Nagasaki, her hometown. She has to go back to help her brothers and sisters clear out their childhood home, which will soon be sold. 

Within the walls of this old house lie the fragments of the Oi family’s history. What remains of memories when families’ secrets are locked away and end up casting a shadow over the collective recollections? Noriko decides to reconstruct the past of her mother Mitsuko, a survivor of the atomic bomb, in the hope of passing down her cultural heritage to her children and healing the dark reminiscences of the tragic past.

But her quest promises to be arduous. Mitsuko, who passed away 30 years ago, has never shared her story. Through her findings, Noriko meets various allies who will help her uncover her mother's past and unveil unknown details about this era of her native Japan.