In her youth Gertrud falls in love with a rising poet, and lives with him for three happy years. Then she notices that he is paying rather less attention to her than to his career. For this reason she leaves him. She has the unrealistic notion that romantic love should last indefinitely and remain as passionate as it was at the beginning (and moreover that it is the one and only thing in life that matters).
From the time she deserts the poet she lives a frustrated life. She marries another man whom she doesn't love (though she still expects him to show a romantic passion for her). Then she leaves him and falls for a young pianist who only wanted her as a temporary mistress and soon gets shot of her. So neither of these relationships brings her any contentment, and she lives the rest of her life in melancholy solitude.
One wonders why Dreyer wanted to give us a portrait of Gertrud. She is not an attractive character. Her inability to benefit from the possibilities for happiness in her own life ruins the lives both of her first love and of her husband, with either of whom she could have had a good home had she not been so self-centred and so unappreciative of anything except romantic passion.
The story is told with clarity and with the careful artistry that we expect from Dreyer, and it is well acted in a stylised way that has obviously been rigorously controlled by the director. Presumably he was satisfied with his achievement. But whereas some of his earlier films attained the level of tragedy, this one, lacking both dramatic incidents and a worthy protagonist, remains dismal.