The Letter tells the story of two young women left alone on a ship on its way to Australia from Wales, after their parents die from an illness that's rife onboard. The younger of the two, Mary, is the ancestor of Gabby, who lives in Bendigo in the 21st century. When her grandmother dies it's left to Gabby and her mother to clear out the house and decide what to do with it. In her grandfather's desk Gabby finds a letter that's been hidden away for generations, and discovers a family secret. Mary and her sister Sarah, both in their teens, face a very uncertain future in a strange country with no family and no friends. When Sarah becomes ill onboard the ship Mary is terrified of losing her as well, while Sarah insists Mary spend as much time as possible away from the tiny cabin in the hope she, at least, will not contact the illness. Mary meets an English gentleman and finds him both charming and kind when he offers to help the girls by introducing her to other well-to-do people, who may be able to help them find employment in the new country. He proves to be no gentleman though and Mary, not wanting to pass her burden to her sister, keeps her feelings and her experience to herself. When they arrive in Australia they are met with all kinds of challenges; making their own decisions is fraught with danger in a country where women are well outnumbered by men, many of whom are convicts. When Gabby, many years later, finds the hidden letter, she discovers Mary's secret and is stunned but proud of what it tells her of her ancestors.