Stephen Gordon
The protagonist of the novel, Stephen is a courageous young woman who was given a boy's name by her parents who were expecting a son and heir. She does not feel like a girl from as long as she can remember; she wants to cut her hair short, wear boy's clothes and become a boy. She does not fit the cookie cutter image that her upper class parents and their social circle require but despite that is very close to her father who dotes on her. She and her mother Anna have a very distant and difficult relationship.
Stephen experiences her first crush at a young age when she is attracted to one of the family's maids, but is upset when she sees the maid kissing her boyfriend a footman at the Gordon home. She falls in love with neighbor Angela, who betrays her by showing a love note she wrote to her husband, who outs Stephen to her furious mother.
Stephen finally finds "the one" - Mary, with whom she drives an ambulance during World War One. During this time she also drives at the front, and is so courageous on the battlefield that she is awarded France's highest honor after the end of the war. She and Mary settle down but when published writer Stephen returns to writing, she becomes a little removed from the relationship. She realizes that she cannot make Mary truly happy and so sacrifices her own happiness by pushing her into the arms of someone else.
Lady Anna Gordon
Stephen's mother is a distant woman who widens the distance between herself and her daughter every time it is apparent that she is not the cookie-cutter upper class daughter that she demands. She believes that her attraction to the same sex is unnatural and it is in some way a blasphemy to call her feelings love, or to compare her love of another woman to a woman's love of a man. At every turn she lets Stephen know that she is not as she should be. Lady Anna loves her husband but is unable to equate Stephen's feelings of love for Angela or Mary to her own feelings for Philip.
Sir Phillip Gordon
Sir Phillip is Stephen's doting father. He wants to understand who his beloved daughter is and so studies new psychiatry writings that focus on "inversion" and homosexuality. He never reveals this study or reading to Stephen because he does not want her to feel that she is any way not good enough for him. Sometimes, given how judgmental his wife is, it is hard to see how the two came to be married in the first place.
Sir Phillip is killed in a freak accident when a falling tree crushes him underneath it.
Martin Hallam
Canadian national Martin is Stephen's best friend. She loves him in a kind of sisterly way, and considers him her best friend, but he has deeper feelings for her and declares his love for her which sends her into a tailspin and derails their friendship. Over the war years they are estranged and have no contact but after the war they run into each other again when Martin is also living in Paris. They re-connect, and rekindle their friendship, but it soon becomes apparent that he is attracted to Mary. The two end up together after Stephen pretends to have an affair and drives Mary into his arms knowing that he can make her genuinely happy.
Angela Crossby
Angela is a bored housewife who has recently married the Gordon's neighbor. She is not homosexual but is fascinated by the idea of a lesbian relationship and considers the kisses that they share to be like a schoolgirl relationship. Angela is also having an affair with another man; when Stephen finds out Angela fears that she will reveal her secret to her husband and so takes a preemptive strike by showing her husband one of the love letters Stephen has written to her, trying to frame the relationship as a one-sided crush.
Valerie Seymour
The lesbian hostess of a Parisian salon, Valerie is more pivotal in Stephen's life than she realizes; when Stephen wants to push Mary into Martin's arms she pretends that she is having an affair with Valerie.
