"Through a Glass Darkly," originally titled "The Wallpaper," is the first part in a film trilogy, the start to a new direction taken by Ingmar Bergman: "chamber films," so named for their analogy to chamber music.
First Movement. The film opens with the mirroring of a gloomy sky on the placid Baltic Sea waters at the Faro Island shores, near Gotland's northernmost tip. Four bathers, all in a jovial mood, splashing and joking, are returning from a swim in the cold sea. As they reach the jetty, the youngest members of the quartet, Karin (Harriet Andersson) and her teenage brother, Fredrik, known as Minus (Lars Passgard), are sent off to get some milk at a nearby farm, while Karin's physician husband, Martin (Max von Sydow), and her father, David (Gunnar Bjorstrand), a writer, go and set up their fishing nets. David has just returned from Switzerland, where he was finishing writing his latest novel, and their task gives them a private opportunity to discuss Karin's status, whose schizophrenia has been diagnosed as most likely incurable.
On the way to the farm, Minus expresses his hope that their father will be successful with his latest novel's publication. On the way back, Minus confides in his sister his sexual apprehensions, which eventually degenerates into his admonishment of Karin for the (maybe) too intimate attention she keeps showing toward him. But most importantly, he confesses how much he wishes he could communicate with his father.
The quartet is reunited for the evening dinner around a table in front of their cottage. Again, a festive atmosphere prevails, but soon turns sour. David confesses that while he was anxious to return to his family after his long absence, that he is about to leave again, in spite of his earlier promise to his children not to travel so often. Somewhat guiltily, and seeking forgiveness, David distributes some presents, all of them turning out to be unsuitable. He goes into the house under the pretense of getting his pipe tobacco, but it is only to release his pent-up anguish at being trapped in his own narcissistic world. When David returns to the table, the family proposes to perform a short play, written by Minus as a gift to his father. The play, "The Artistic Haunting" or "The Tomb of Illusions," tells of a prince who chooses world fame over love. This, of course, strikes too close to David for comfort, but he nevertheless applauds.
Readying themselves for bed, Karin and Martin discuss the evening, and Karin turns down her husband's tender advances. But later in the night, the cry of gulls awakens her and, following her inner voices, she steals out of the room to an abandoned upstairs room. In the room, she presses her ear to the wall, listening to voices emanating from behind it. She moves to the center of the room, falls to her knees in ecstasy, and achieves a sexual climax. Karin descends to her father's room, where he is still putting some last touches on his novel. He carries her to his bed, tucks her in, and she falls asleep. Minus appears standing on the window sill, and asks his father to come and join him in retrieving the nets. Some time after their departure, Karin awakens. Rummaging in David's desk, she finds his diary, which she opens toward the last written pages and reads, "Her illness is incurableI'm horrified by my curiosity, by my urge to record its course, to make an accurate description of her gradual disintegration, to use her." Karin is crushed by her discovery. She returns to her bedroom and tells her husband about some of her findings in David's diary. But she cannot bring herself to tell him that David is actually studying her descent into madness. Martin tries unconvincingly to reassure her.
Second Movement. Karin and Minus are alone. Minus is "studying" his Latin book, into which he has hidden a girlie magazine. Karin uncovers the subterfuge and teases him about it. In this moment of familiarity, Karin tells Minus her terrible secret, her experience in the room upstairs, and takes him to the room. She explains her experience with the voices she hears from behind the flower wallpaper. She tells him how she passes through the wall into an adjacent room where people are waiting for "Him." Karin further confesses to Minus that she has sacrificed Martin for the "other." On the other hand, somewhat lucidly, she states she is not sure this is all real.
Some time later, Minus is looking desperately everywhere for Karin, who has disappeared from his sight. At last, he finds her lying down inside the hull of a beached boat wreck. Minus approaches Karin, who is lying on the boards in a fetal position, and leans over her. Karin, with a devilish grin on her face suddenly reaches for him, and forces him against her in a passionate embrace. We guess from the next scene, where Minus is holding Karin in his arms that incest has occurred.
Meanwhile, David and Martin, who went by motorboat to Gotland, have anchored the boat and are having lunch. Martin confronts David's having written in his diary about Karin and her sickness. What follows is a disturbing exchange of accusations. David admits to studying Karin and her illness as a subject for his next book, but doesn't Martin wish at times for Karin's death? David confesses that recently in Switzerland, he tried to commit suicide, but fate (God?) intervened and saved him. At that moment, David manages, for the first time, to communicate his inner most feelings:" From the void within me, something was born that I can't touch or name. A love. For Karin. For Minus. For you."
David and Martin, returning to their island, are greeted at the pier by Minus, who tells them about Karin's latest crisis. They all run to the shipwreck. As Karin expresses her wish to talk privately to her father, Martin is vexed and possibly guesses what happened between the two siblings. He leaves to go get an ambulance for Karin. Karin tells her father that she is giving up "living in two worlds," and wants to be committed. She also hints unambiguously at the incest. David's transformation continues as he confesses his guilt to Karin.
Third Movement. Karin is in her room, packing her bags. As Martin goes to fetch some medicine for her, she slips away to the abandoned room upstairs. When David and Martin find her there, she is standing in the middle of the room talking to "them." Martin enters the room and Karin tells him to rejoice at God's imminent arrival. She tells her husband to come and kneel with her, to wait for God to appear. The helicopter ambulance arrives in a roar of engine and whirring blades that makes the house shake and the closet door open. Through the window, we catch a glimpse of the helicopter landing like a giant spider suspended by an invisible thread. Suddenly, Karin is overwhelmed by her vision of the spider-God. She run down stairs and is stopped by Minus, thus allowing Martin enough time to inject her with a sedative. As she calms down, she describes her vision of a horrifying "spider-God" who tried to penetrate her. The ambulance nurse knocks at the door. Karin puts on her sunglasses, as if they were a symbolic of cutting herself from the world, and calmly walks to the waiting ambulance.
Following his sister's departure, Minus enters his father's room for the first time. Minus tells him of his panic over going on living, after the latest happenings. David's answer to his son is that he can live if he can hold unto something. "I do not know if love is proof of God's existence, or if love is God himself," says David, but, "that thought helps me in my emptiness and my dirty despair." After some more exchanges, as David leaves the room to prepare dinner, Minus, in near ecstasy says, "Papa spoke to me."