In the midst of World War II, an English musician, Norah Chambers, places her eight-year-old daughter, Sally, on a ship leaving Singapore, desperate to keep her safe from the Japanese army as they move down through the Pacific. Norah remains to care for her husband and elderly parents, knowing she may never see her child again.

Sister Nesta James, a Welsh Australian nurse, has enlisted to tend to Allied troops. But as Singapore falls to the Japanese, she joins the terrified cargo of people, including the heartbroken Norah, crammed aboard the Vyner Brooke merchant ship. Only two days later, they are bombarded from the air off the coast of Indonesia, and in a matter of hours, the Vyner Brooke lies broken on the seabed.

After surviving a brutal 24 hours in the sea, Nesta and Norah reach the beaches of a remote island, only to be captured by the Japanese and held in one of their notorious POW camps. The camps are places of starvation and brutality, where disease runs rampant. Sisters in arms, Norah and Nesta fight side by side every day, helping whoever they can, and discovering in themselves and each other extraordinary reserves of courage, resourcefulness and determination.