In 1837, Elisabeth Laurier, a French-speaking Swiss governess, agrees to bear a child for an anonymous English landowner to raise funds for her father’s debts. They meet over three nights at a coastal hotel, and though they seek distance, their time together grows into a deeply passionate connection by the warmth and glow of firelight. Nine months later (10 August 1838), Elisabeth gives birth to a daughter and, as agreed, relinquishes her to the care of the father. Over the years, Elisabeth never forgets her child and keeps a journal of watercolored flowers and plants, adding a page for each holiday and each birthday her daughter celebrates while they are apart.
The anonymous Englishman is Charles Godwin, a landowner and struggling sheep farmer who can barely keep at bay the creditors driven by his philandering father, Lord Clare. Charles’s wife, Amy Godwin, is paralysed and catatonic due to a horseriding accident. Amy’s sister, Constance, runs the Godwin household.
Seven years after Elisabeth’s arrangement, she becomes the new governess for the child, who is named Louisa. Elisabeth has chosen this path knowing that Louisa is her daughter. Initially, Charles rejects Elisabeth and orders her to leave, but Constance insists he grant her a month to adjust. Charles makes Elisabeth swear never to reveal to Louisa or anyone the nature of their previous relationship.
Louisa is a spoiled, ignorant, and wilful girl, loved by no one except her father. Elisabeth is determined to teach her how to behave and to secure an education so she can choose her own path in the world. To win Charles’s support, Elisabeth promises that she will never harm the girl, and whatever she does to Louisa she will do to herself. At the same time, Elisabeth receives but declines a marriage proposal from an American rancher staying with the Godwins.
Outside of lessons, Louisa spends all her spare time in the lakehouse, a small belvedere on the estate in the middle of a lake accessible only by boat. Louisa pretends she has a mother, and Elisabeth initially watches from the jetty as Louisa plays inside the lakehouse. She also notices that Charles swims naked there in the mornings, and she begins to watch him as well, leaving before he can be seen. In the classroom, Elisabeth paints picture cards to teach Louisa to read and tells her a tale about the firelight to help her concentrate on her studies.
A growing attraction leads to a sexual relationship between Elisabeth and Charles. He even speaks of leaving everything behind with Elisabeth, but she knows it is impossible given his obligations to the estate, family, and wife. Meanwhile, the estate is appraised for sale to cover debts. On a bitterly cold night, Charles grapples with his conscience as he considers Amy’s fate. He opens her window, removes her covers, and lets the fire burn out, causing Amy to die of exposure. After Amy’s death, Constance admits she has grown close to Charles, though they cannot marry; she concedes defeat when, at Amy’s funeral, she realizes the depth of Charles’s feelings for Elisabeth. Elisabeth confronts Charles and asks whether he killed Amy, and he admits it. They both feel guilt, but neither expresses regret.
Soon after, Louisa discovers Elisabeth’s room and finds the illustrated journal dedicated to “My English Daughter.” Elisabeth confirms to Louisa that she is her mother. After the Godwin estate is sold, Charles, Elisabeth, and Louisa leave on a snowy day to begin a new life together as a family.
