Sam Kimura, a Japanese American veteran of World War II, learns that his sister Kei, whom he has not seen in nearly sixty years, has passed away. As Sam peruses items left by Kei for him, her memory transports him back to the Salinas, California. He recalls the turbulent events that led to his family’s evacuation from their farm to the wastelands of Wyoming in the Heart Mountain internment camp.
At Heart Mountain, the Kimuras, including their grandfather Ojii-san, suffer under the harsh conditions of camp. Sammy joins the Japanese American Citizens League (JACL) as a camp leader under the direction of its National Secretary, Mike Masaoka, and finds friendship and companionship with a volunteer quaker nurse, Hannah. Sammy and Masaoka call for patriotism and rededication to America to demonstrate Japanese American loyalty. This rubs many in camp wrong, including Sam’s father, Tatsuo. Meanwhile, Kei, liberated from her daily farm chores and family obligations, finds her voice and a budding romance with Frankie, an agitator in the camp.
Meanwhile, Masaoka has organized the 442nd all-Japanese American regimental combat team and announced that he will be its first volunteer. He invites Sammy to join him, but Tatsuo rejects the idea when the government circulates a “Loyalty Questionnaire.” Sammy argues with his father, who has threatened to refuse to repledge his Allegiance.
Sammy tries to bring the camp together with a dance, but the night is hijacked by Frankie, who uses the occasion to stir opposition. Outside the dance, Sammy is beaten up as one of Masaoka’s perceived stooges. He seeks medical help from Hannah, and in a moment of rare privacy, the two share their feelings for one another.
After answering “no” on the Loyalty Questionnaire, Tatsuo is arrested to be taken away to Tule Lake, a punishment camp for disloyals, while Sammy against the wishes of his older sister Kei, heads off to training camp to prepare to fight in the war.
While Sammy trains at camp, Kei and Frankie lead the resistance to the draft at Heart Mountain. Masaoka, seeking to highlight the valor of 442nd, picks Sammy as its poster boy, and his picture graces the cover of Life Magazine, even as Tatsuo’s condition at Tule Lake deteriorates.
As a JACL spokesman, Sammy calls for the arrest of the resistance, while Hannah seeks to aid the resistance and hide Frankie from the authorities in camp, leading to a violent crackdown. While Sammy and his unit are sent out to rescue a battalion of trapped caucasian soldiers, suffering enormous casualties, Kei receives life-changing news from Frankie in prison.
When the war ends, Sammy is offered a job with the JACL in D.C. Sammy demurs so he can return to his family, now in San Francisco. But when he learns the awful truth of what has transpired since he left camp and of the choices his sister Kei has made, his happy reunion with her is tested, and in that fateful moment, the course of the rest of his life is set. Only Kei’s final efforts to reach through, from beyond her grave, can hope to provide Sam with a second chance to find redemption and forgiveness.