The Swedish queen makes peace, falls in love with the Spanish ambassador, and abdicates her throne. Her philosophical character and the events are historical with the major exception of the romance.
When King Gustavus is killed in 1632, his child Christina is crowned queen by Chancellor Oxenstierna (Lewis Stone). Sixteen years later after the victory of Prince Charles (Reginald Owen) in which 10,000 Swedes died, Queen Christina (Greta Garbo) rejects calls for vengeance and glory to sign a peace. Aage (C. Aubrey Smith) finds Christina reading a book early every morning. The people want her to marry Charles but know she prefers the Treasurer Count Magnus (Ian Keith), who kisses her when he gets the chance.
Christina tells Ebba (Elizabeth Young) they will go away for two days, but the queen discovers that Ebba resents Christina's domination. A disappointed French ambassador asks the queen to sign an agreement, because the Spanish ambassador is arriving. Christina dislikes wars and wants to remake the world. She tells Oxenstierna she does not wish to marry, and she questions her love for Magnus. Dressed as a young man, Christina helps the coach with the Spanish ambassador Antonio (John Gilbert). They dine together at an inn and agree to share the last room. As they undress, Antonio realizes she is a woman. They share the bed; Christina is happy and memorizes the room.
Christina gives Ebba permission to marry. On her throne she receives the Spanish ambassador and wants to learn of their art and science. He is angry at a private meeting because his job is to ask her to marry King Phillip; but she pacifies him and refuses to see Magnus. People resent the Spanish and go to the palace. Christina says she won't marry Charles and asserts her freedom. She tells the general to let the people in and persuades them to let her govern. Antonio is attacked in the street but is rescued by Magnus. The jealous Magnus asks Christina to send Antonio away, and she agrees, giving him a passport. Antonio and Magnus arrange to meet beyond the border for a duel. Oxenstierna tells the queen to do her duty and marry Charles; but she rejects the marriage and abdicates her throne to him. Antonio and Magnus fight with swords, and Christina travels by coach and horse to board her ship, where she finds Antonio dying. Nonetheless she decides to sail for Spain.
This film emphasizes the romantic theme that even a queen has the right to choose her own mate. The historical Queen Christina was tutored by Descartes and abdicated her throne because she converted to Catholicism in addition to not wanting to marry.