The time: 1972. The place: Granton, Alberta. Naomi Nakane is a 36-year-old middle school teacher. One day, she's saved from her boring class by an important phone call. It's bad news. Her uncle is dead.
Naomi's aunt (the Japanese for "aunt" is "obasan") is super old. She's also alone: her husband just died. So Naomi does what any good niece would do: she pays her a visit.
Obasan seems strangely unperturbed about Uncle's death. Even though Naomi keeps asking her about it, Obasan seems to have nothing to say. Naomi tries to get her to rest, but Obasan's not budging. They go into the attic instead.
This is where the story really begins. Naomi remembers her own past in the internment camps and how her mother disappeared one day without any explanation. When Obasan finds a package from Aunt Emily (her other aunt, not Obasan), things really get interesting.
It's a huge stack of papers. Aunt Emily's letters, journals, and papers lead Naomi on a wild ride through her childhood. She remembers her mother. Her beautiful house. The neighbor who molests her. Basically, she remembers all the things about her childhood that she wanted to forget.
Naomi was pretty young when the war starts, so she doesn't remember very much. Aunt Emily's papers fill in the gaps. Through her words we see the horrors of the internment camps, the helplessness of the Japanese Canadian community, and the hysteria taking over the country. Naomi's mother leaves to take care of a relative in Japan, and various family members are taken to internment camps.
Aunt Emily's journals last until the family is forced to leave to Slocan, a remote town. Naomi can remember Slocan but she still wasn't old enough to understand all the things that happened while she was there. She's especially mystified by what could have happened to her mother.
Slocan is a town full of racism and prejudice. Nearly everyday is a struggle, just to get to school. But the family cobbles together a semblance of a life there, and they manage to find a bit of peace and happiness.
But disaster strikes again when Naomi's father dies. And then, one day, the family is exiled. That's right, they are exiled from their place of exile. Apparently one exile wasn't enough.
They move into a one-room hut on a sugar beet farm. By now Naomi is old enough to hate everything. Seriously, everything. It is all so horrific—the backbreaking labor, the heat and the filth—that she barely remembers anything. She successfully blocks most of it out. When the Japanese Canadians are set free, her family moves out of the hut and into the town.
Fast forward to the present day. Everyone is in Obasan's house for Uncle's funeral when something happens. An old letter reveals the truth about Naomi's mom. She was a victim of the Nagasaki bombing. She didn't want her children to know about her suffering, so she swore Aunt Emily to secrecy. Everyone is shaken by the news.
The book ends where it begins. Naomi is in Uncle's valley, looking at the river and the flowers. But there is one difference: now she knows why her Uncle came there so often. She can feel the peacefulness.