In 1943, during the Second World War in Burma, Lieutenant Peter Dillon is fatally wounded during an ambush in the jungle. Before dying, he is executed by a Japanese officer and his watch is taken from his lifeless body.

Decades later, in 1989, Peter's nephew, James Dillon, falls in love with Masako Takahashi, a Japanese woman living in London. Their engagement causes tension within James's family, especially with his mother Sarah. Still haunted by the war, Sarah holds a deep grudge against the Japanese for the death of her childhood sweetheart and brother-in-law, Peter.

As James and Masako plan their wedding, they discover a connection between their families' pasts. In 1907, James's grandfather, Edward Dillon, visited Japan and befriended Kanou Takahashi, Masako's grandfather, who owned a ryokan. Their friendship ended during World War II when Japan attacked Pearl Harbor. Kanou's sons Kazuo and Takeshi became officers in the Japanese army, while Edward's sons John and Peter served in the British army. All four of them fought in Burma. Both Kazuo and Peter were killed.

James finds evidence suggesting that Takeshi may have killed Peter. Masako learns that her father carried shame for his actions during the war, which led to his eventual suicide. Meanwhile, James discovers that his father, John, commanded rearmed Japanese soldiers in Saigon after the war, one of whom was Takeshi. Surprisingly, John chose not to find out if Takeshi was responsible for Peter's death because he saw how much the war had changed him. Takeshi also saved his life from an assassination attempt.

Tensions arise when Masako finds that the watch her father left her holds proof that he did indeed kill Peter, causing James a moral dilemma. However, after speaking to their fathers’ old comrades, James and Masako decide to reveal their families' histories to their mothers. Sarah struggles at first but softens when she learns that her husband, John, respected Takeshi and forgave him for his actions during the war.

The couple gets married in Kyoto, symbolising reconciliation between their families. Even Sarah and Masako's mother, Yoko, find common ground. After the wedding, Sarah meets Goro Harada, a former Japanese officer who served with her husband in Saigon. Through his respect for John and honest reflections on the past, Sarah is finally able to let go of her anger.

James and Masako's marriage becomes a testament to forgiveness, understanding, and the healing power of love. It not only brings their families together but also confronts the painful legacies of war, offering hope for a future free from the burden of hatred from the past.