Set at the beginning of the World War II, when Polish cavalry still fights with lances against the first German infantry. The film follows the winding paths of Lotna, a snow white horse, as she wanders through Poland during it's fight against the Nazis in 1939. The story opens as a Polish officer buys Lotna from a dying landowner. The two ride off, but the captain is killed. She then goes to an ensign who is stationed with his company in a tiny town. The ensign marries a local schoolteacher, but on their wedding day a retreating regiment of Polish infantrymen travel through the village. The next morning, the mare runs away and as the ensign tries to stop her, he is shot. Lotna is then found by a lieutenant who rides her in a valiant charge against the German invaders. He dies, and Lotna is taken by a sergeant-major who finds her guarding the fallen officer. The officer rides the horse so hard that she breaks a leg and he must shoot her. He buries the mare under a lone pine tree.