We see Sebastian’s mansion lit up for the party. Inside, Alicia is putting on earrings when she spots the keys to the wine cellar sitting on a table in Sebastian’s room. As she goes to grab them, Sebastian speaks to her from the other room about his surprise that Mr. Devlin is coming to the party. “I just hope that nothing will happen that will give him any false impression,” Sebastian says, as Alicia takes the key off the keyring. Sebastian comes out of the closet and takes Alicia’s hands, which she keeps closed in fists to hide the stolen key. He tells her that he trusts her, but that at his age, “every man that looks at your woman is a menace.” He goes to kiss each of Alicia’s hands, but she throws her arms around his neck before he can see the key, dropping it on the floor intentionally and kicking it under a chair.
The scene shifts to the party in full swing, with gentle music playing. Sebastian and Alicia greet their guests. The camera zooms in on Alicia’s fist, which holds the key. She waits for Devlin, but he doesn’t show, and Sebastian beckons her into the other room, insisting that all their guests have arrived and looking at her knowingly. She walks with him into the other room just as Devlin is arriving. In the next room, Alicia spots him and goes over to greet Devlin. As he kisses her hand, she slips the key into his hand. Sebastian notices them saying hello and goes over to greet Devlin. After a brief exchange, Sebastian goes to greet another guest at the party, and Devlin and Alicia walk around the room. “This isn’t going to be easy,” Devlin whispers to Alicia, citing the fact that Sebastian is sensitive and jealous and that he will watch the two of them all evening. When Devlin says that he hopes they don’t run out of wine and have to go down to the cellar for more, Alicia becomes anxious, having not thought of that.
They go into the next room where the bartenders are serving drinks. Alicia hands him a glass of champagne as a woman comes up and greets Devlin. She recognizes him and greets him demonstratively, taking his arm and leading him away from Alicia into the other room. Alicia looks down at the champagne bottles and asks Joseph the butler if he thinks they have enough champagne to last the whole party. He tells her that he doesn’t know and Alicia anxiously walks into the next room. In the next room, she sees her husband engaged in conversation and takes her chance to have a private chat with Devlin, who excuses himself from his conversation with the woman. Alicia and Devlin sit to chat with one another, and Sebastian waves to them from across the room. While the duo pretends to laugh and engage in light party chatter, Alicia informs Devlin that they are running out of wine faster than they thought and that the bartender might have to ask Sebastian for more wine. Alicia instructs Devlin to wait for her in the back so that she can show him the wine cellar door, just as Sebastian begins walking towards them.
Devlin excuses himself and goes into another room and Alicia goes to greet Sebastian, who compliments her on her role in throwing the party. In the next room, Devlin lights a cigarette and looks at the stock of champagne in the nearby barrel. Meanwhile, Alicia notices that more and more champagne glasses are being distributed, and anxiously excuses herself from a conversation with Sebastian and several others to go and ask the musicians to play some Brazilian music. Outside, she meets Devlin and directs him to the door to the wine cellar. She tells him that she’ll keep the garden door open and warn him if anything happens. Alicia goes outside as Devlin goes down to the wine cellar and snoops around. Standing in the doorway, Alicia wears an anxious expression. Meanwhile at the party, the bartender looks at the champagne bottles on ice. In the cellar, Devlin looks at the various bottles, accidentally knocking one off the shelf and onto the floor.
Hearing the crash of the wine bottle, Alicia runs to the cellar to see what has happened. Devlin points out that the bottle he dropped was filled with sand. He tells Alicia that they have to leave the room the way they found it and instructs her to find bottles with the same label as the one filled with sand. Devlin tells her that he thinks it’s some kind of “metal ore” and he collects some in a small envelope. Upstairs at the party, only three bottles of champagne remain, and the bartender goes to alert Sebastian. In the cellar, Alicia is anxious to get out of there and clean up, but Devlin remains cool and sarcastic. At the party, Joseph the bartender approaches Sebastian and informs him they are running low on champagne, just as Devlin and Alicia leave the cellar. As they shut the door behind them, Alicia becomes paranoid that Sebastian has seen them, as Devlin kisses her passionately in the dark backyard. He wants Sebastian to think they have stolen away to kiss, so as to deflect him from the problem with the wine cellar.
Sebastian and Joseph stop on the stairway, watching the couple kiss in the backyard, and Sebastian sends Joseph back up to the bar. Alicia whispers Devlin’s name as he kisses her, and as Sebastian nears the door, Devlin instructs Alicia to push him away. When Sebastian interrupts them, Alicia tells him that Devlin has been drinking and forced himself on her. Unconvinced, Sebastian accuses Alicia of being in love with Devlin, but she denies it. Devlin says, “For what it’s worth, as an apology, your wife is telling the truth. I knew her before you, loved her before you, but I wasn’t as lucky as you.” Devlin leaves, and Alicia tells Sebastian that Devlin had threatened to make a scene if she did not agree to see him alone. Coldly, Sebastian tells Alicia to go back upstairs and be with their guests.
Upstairs, Madame Sebastian asks Devlin why he is leaving so soon, and he tells her he has to be up early in the morning and leaves. Sebastian gets Joseph and they go down to get the wine. When Sebastian takes out his keys, he finds the key to wine cellar missing. He says nothing to Joseph, advising them to make do with the wine that they have remaining upstairs. Later, when the party is over, Alicia apologizes for letting Devlin kiss her, but Sebastian will not hear it, and apologizes for behaving so jealously. Alicia invites him upstairs, but he tells her that Dr. Anderson is waiting for him. Alicia climbs the stairs to bed and Sebastian watches her menacingly. The scene shifts to later that evening, as Sebastian comes into the bedroom. Taking off his jacket, he looks over at Alicia asleep in her bed, then pulls out his keychain and looks at it. We see the clock chiming late at night, and Sebastian looks over from his bed at Alicia, asleep in hers. Rising from his bed, Sebastian puts on his robe and goes back to his night table, finding the key returned to the keychain.
Sebastian goes to the wine cellar and examines the shelf. He looks at the drain in the sink and notices a splatter, then goes to look at the bottles on the shelf. Going down the line, he examines the years on the wine, before picking up one labeled “1940.” He holds it up and looks at the sand inside. When he goes to open the top of the bottle, he finds that the wrapper is loose and broken, as suspenseful music plays. Looking down at the floor, he finds grains of sand as well as some glass from the bottle that Devlin and Alicia broke. The label from the broken bottle reads “1934.” Sebastian goes upstairs. He sits in his mother’s room and wakes her up. When she awakens, he asks for her help, telling her that Alicia is up to something. A smile spreads across his mother’s face, and when she asks if it is Mr. Devlin, he informs her that he is “married to an American agent.” Madame Sebastian’s face falls as she realizes the gravity of the situation, and she reaches for a cigarette from a box on her bedside table.
We see Alicia asleep in her bed. In her room, Madame Sebastian speaks to her son, who is despondent at his having been duped by the Americans. “Stop wallowing in your fallen memories,” his mother scolds. He sits down on the bed, worrying that he will be punished by the Nazis when they realize he has married an American spy. “Look what they did to Emil Hupka,” he says, “I bungled and there’s no excuse.” Madame Sebastian tells her son that there is no reason that the Nazis have to find out, and when Sebastian bemoans the fact that Mathis already doesn’t like him, his mother assures him that they would never expect him to have married an American agent; “We are protected by the enormity of your stupidity, for a time,” she says. Sebastian suggests that he should kill Alicia himself, but his mother urges him to calm down lest he lead the others to be suspicious. She tells him that she will take care of Alicia, that Alicia can learn nothing more and that “she must go, but it must happen slowly…if she could become ill, and remain ill for a time, until…” The screen fades to black.
In this section of the film, matters become a great deal more suspenseful, as Alicia steals a key from Sebastian and plots to break into his wine cellar to learn more about the Nazi's plot. Hitchcock continues to align the viewer with Alicia, shooting her clenched fist in tight close-up as she clutches the stolen key. As Sebastian goes to kiss her hand, she throws her arms around him to distract him from the secret she is hiding in her fist. Then, in the next scene, as the party begins, the camera starts at the ceiling, taking a birds' eye view of the party, before zooming in slowly on Alicia's fist, still clenched. In the midst of the liveliness of the party, the viewer is privy to her potentially-fatal secret, hidden in the palm of her hand.
An irony in this section of the film is the fact that Sebastian is suspicious of Alicia and Devlin, but not because he suspects them of spying on him, but because he is afraid that they are in love. They are in love, it’s true, but the greater threat is that they are plotting to expose his plot and give information to American intelligence. Indeed, when Sebastian finds them in the cellar, Devlin manages to take him off their trail by kissing Alicia passionately in plain view of him. Devlin knows that if they keep Sebastian suspicious of their love affair rather than their status as spies, they will be safer in the long run.
Complicating matters even further is the fact that Devlin and Alicia are in love. Alicia must lie to Sebastian, telling him that Devlin's love for her is a one-sided unrequited affair, and that she does not return his affections. The viewer knows that this is not the case, that the feelings between them are far more complicated than just a crush that Devlin has on her. Given this complication, Devlin and Alicia must keep layering their deception, playing different parts at different times. Not only are they performing for one another—neither Devlin nor Alicia is quite willing to confess their feelings—but they are performing for a man who would kill them if he knew.
Indeed, Sebastian is the villain of the story, all the more evil because he has such a strong connection with his diabolical mother. Madame Sebastian's joy at hearing that Alicia is betraying Sebastian is almost comical, a disturbing heightening of the idea that “mother knows best.” She scolds her son for being so upset about the betrayal of his wife, reaching for a cigarette and plotting their next move, like an elderly Lady Macbeth. She is less of a maternal figure and more of a coach, encouraging him to be ruthless and unsentimental about the difficulty of his plight, all the while denigrating him for being so easily duped.
After being aligned with Alicia's perspective and plight for so much of the film, it is notable that the viewer's perspective shifts at this part of the film, and we witness Sebastian and his mother's response to learning of her betrayal. After spending so much of the film privy to the American perspective, we are suddenly clued in to the secretive machinations behind enemy lines. Sebastian and his mother prepare a way of killing Alicia that is slow and almost imperceptible, held secret from both Alicia and Sebastian's Nazi cohorts, who would surely kill him if they knew.