The third entry in Ingmar Bergman's trilogy about faith and redemption (with Through A Glass Darkly and Winter Light) is a stark and enigmatic allegory fueled by subtle performances from Ingrid Thulin and Gunnel Lindblom.
Thulin plays Ester, a translator and intellectual, who is traveling back to Sweden on a train with her younger sister Anna (Linblom) and Anna's son Johan (Jorgen Lindstrom). They stop in the town of Timuku and check into an old hotel in a foreign land where the language cannot be understood by the three travelers.
Ester, who suffers from a terminal lung disease, is very protective towards Anna; but Anna resents being tied down by her sickly sister, and she leaves the hotel room, picking up a waiter (Birger Malmsten in a nearby café. Returning to the hotel room, Anna tells Ester about her sexual encounter with the waiter, and Ester becomes sexually aroused.
Anna leaves for another room in the hotel to continue making love with the waiter. Johan helps Ester track Anna down Anna, and Anna and the waiter proceed to make love a third time. This provokes a violent and biter argument between the two sisters.