Dr. Rivers is a compassionate doctor, who helps traumatized soldiers remember and recover from their war experiences. Although he helps many, he is conflicted about his work. After his patients recover, he is duty bound to recommend their return to the war—a war he comes to oppose.
Siegfried Sassoon is a rich, aristocratic army officer and talented poet; he lands at Craiglockhart after he writes a Declaration in fierce condemnation of the war. War supporters want to keep Sassoon at the hospital so he can't publicize his views. Eventually Sassoon returns to the war out of a sense of duty, but he never changes his views about it.
Billy Prior is a young working-class man, who was promoted to an officer's rank when he served at the front. He arrives at Craiglockhart after war traumas leave him temporarily mute. Prior is intelligent, sharp-witted, and acutely aware of class bigotry in Britain. While Rivers treats him, Prior challenges and questions the psychiatrist at every turn—sometimes just for the pleasure he derives from doing so.
Wilfred Owen is a young and fairly innocent soldier, as well as a brilliant poet. At Craiglockhart Owen is treated for the stammer he developed at the front. Owen edits the hospital's patient publication and meets Sassoon, who becomes his mentor. Sassoon encourages Owen to polish, and publish, some of his most searing poems against the conflict.
David Burns is a young officer sent to Craiglockhart for treatment. Dr. Rivers tries to help him but has little success. Burns is too stressed to speak about his terrible war experiences; his reticence prevents him from releasing his memories and recovering. Unable to eat, he is gaunt and emaciated, like a "fossilized schoolboy."
Anderson is a trained surgeon, who worked at frontline hospitals during the war. His experience has left him unable to tolerate the sight of blood. Anderson is tormented not only by his traumatic experience at the front but also by worries about whether he'll be able to resume his career.
Sarah Lumb is an outspoken and tough-minded working-class woman who works in a munitions factory. Like her mother, Sarah is keenly aware of the limitations placed on women of her class and the problems they often have to live with, especially those involving men. After she meets Billy Prior, the two seem to form a mutually supportive relationship.