On a Pan American World Airways plane to Rio de Janeiro with him, Alicia is impatient to know any "hints" involving her unspecified job in Brazil. She learns that Devlin's boss, the leader of the Allied espionage team named Paul Prescott (Louis Calhern), received information during their last stop that Alicia's father committed suicide and died that morning - he took a poisoned capsule in his jail cell. Saddened, she reacts in full close-up and speaks of the disastrous effects that her father's traitorous behavior has had on her. His betrayal caused her to lack self-respect and she became a self-destructive, hard-drinking, promiscuous, 'notorious' playgirl:

I don't know why I should feel so bad. When he told me a few years ago what he was, everything went to pot. I didn't care what happened to me. Now I remember how nice he once was. How nice we both were, very nice. It's a very curious feeling as if something had happened to me and not to him. You see, I don't have to hate him anymore or myself.

She is somewhat relieved - no longer does she have to hate her father for what he did.

Devlin conceals his reaction to her memories and his growing interest in her. Instead, he informs her of their arrival in Rio. In an outdoor cafe while waiting for her assignment and orders to begin, Alicia asks about the particulars of her assignment and her living situation. She also demands a cook. She refuses another drink: "No thank you, I've had enough...I'm practically on the wagon. That's quite a change." Although Devlin compliments her sobriety, he dismisses it as only a "phase" - he is wary of the former playgirl's lurid reputation. Their conversation turns amorous, as she teases and berates the cool, indifferent, distant, and sometimes nasty Devlin about his unflappable, repressed romantic emotions. Alicia is tremulously hopeful that his faith in her will be renewed, now that she is changing into a new woman and becoming transformed from her former image:

Alicia: You don't think a woman can change?
Devlin: Sure. But change is fun, for a while.
Alicia (contemptuously): For a while. What a rat you are Devlin!
Devlin: All right. You've been sober for eight days. And as far as I know, you've made no new conquests.
Alicia: Well, that's something.
Devlin: Eight days. Practically white-washed.
Alicia: I'm very happy here. Why won't you let me be happy?
Devlin: No one is stopping you.
Alicia: Why don't you give that copper's brain of yours a rest? Every time you look at me, I can see it running over its slogans: 'Once a crook, always a crook,' 'Once a tramp, always a tramp.' Go on. You can hold my hand. I won't blackmail you for it afterwards. Scared?
Devlin: I've always been scared of women, but I'll get over it.
Alicia: Now you're scared of yourself. You're afraid you'll fall in love with me.
Devlin: That wouldn't be hard.
Alicia: Oh now, careful, careful.
Devlin: You enjoy making fun of me, don't you?
Alicia: No Dev, I'm making fun of myself. I'm pretending I'm a nice, unspoiled child whose heart is full of daisies and buttercups.
Devlin: Nice daydream. Then what?
Alicia: I think I will have another drink.
Devlin: I thought you'd get around to it.
Alicia: Make it a double...Why won't you believe in me, Devlin - just a little? Why won't you?

As they sightsee and tour around the city, she teases and mocks him for being afraid of falling in love with her. Alicia constantly baits him by tearing herself down. She calls herself a "little drunk" and a "no-good gal":

I know why you won't, Devlin. You're sore. You're sore because you're falling for a little drunk you've taken in Miami and you don't like it. It makes you sick all over, doesn't it? People will laugh at you. The invincible Devlin, in love with someone who isn't worth even wasting the words on. Poor Dev, in love with a no-good gal. It must be awful. I'm sorry.

Devlin, whose feelings are growing for Alicia but fights against falling in love with her, passionately grabs and kisses her.

In the US Embassy, Devlin's superior Prescott announces that Alicia will be the perfect confederate. She is a promiscuous woman who can lure gentlemen for their knowledge and power with her sexuality: "Gentlemen, I assure you, she's the perfect type for the job...She's good at making friends with gentlemen, and we want somebody inside his house, in his confidence." Devlin is concerned that he hasn't yet told Alicia "the nature of the work" that specifically involves the enemy leader (a "Farben man"), a neo-Nazi scientist named Alexander Sebastian (Claude Rains).

The film is known for having at the time of its production 'the longest kiss in film history.' [Director Alfred Hitchcock circumvented the Hollywood code limiting a kiss to three seconds by interrupting the kiss every three seconds, but they never once break their embrace.] The famous marathon kissing scene between Devlin and Alicia in her apartment lasts almost three minutes, beginning on a scenic Rio balcony, entirely shot in a tight closeup of their faces. They rapidly alternate passionate, clinging kisses and whispered endearments, first on the balcony over the beach, and then continuing with nibbling bites and nuzzling hugs as they walk from the balcony to the telephone and then to the front door. All the while during the sexual seduction, they discuss dinner, hold on to each other, and carry on a conversation:

Alicia: It's nice out here. Let's not go out to dinner. Let's stay here.
Devlin: We have to eat.
Alicia: We can eat here. I'll cook.
Devlin: I thought you didn't like to cook.
Alicia: No I don't like to cook, but I have a chicken in the icebox and you're eating it.
Devlin: What about all the washing up afterwards?
Alicia: We'll eat it with our fingers.
Devlin: Don't we need any plates?
Alicia: Yes, one for you and one for me.
Devlin: You mind if I have dinner with you tonight?
Alicia: I'd be delighted. Where are you going?
Devlin: If you're going to stay in, I have to telephone the hotel, see if there are any messages.
Alicia: Do I have to?
Devlin: I have to. (They walk inside to the telephone where he dials the hotel for messages.)
Alicia: This is a very strange love affair.
Devlin: Why? (she kisses him)
Alicia: Maybe the fact that you don't love me.
Devlin: (He kisses her) ...When I don't love you, I'll let you know.
Alicia: You haven't said anything.
Devlin (kissing her): Actions speak louder than words.

During the middle of their lengthy embrace and love scene, Devlin receives a phone message that Prescott wants to see him "right away" about Alicia's "assignment." Devlin leaves while Alicia prepares their dinner. At the Embassy, Devlin slaps his hand on the table, objecting to Alicia's assignment to woo Alexander and pretend to love him. He resists using her as an undercover agent to infiltrate Sebastian's organization. He argues that she lacks experience and training in that kind of work, although he knows otherwise:

I don't know if she'll do it...Well, I don't think she's that type of woman.

But then Devlin is told that Alexander is known to her and was once a former rejected suitor of hers. He had once fallen in love with her. The Embassy expresses the urgency of its mission: "Sebastian's house is a cover-up, for whatever this Farben group's up to here in Rio. We've got to get Miss Huberman inside that house and find out what's going on there." As Devlin departs, he leaves behind a bottle of champagne on the table that he was planning to take to her. [The bottle left behind is symbolic of their relationship, now cold, forgotten and forbidding.]

Back at Alicia's apartment where she is bubbling over with happiness and preparing a chicken dinner, she greets him for more kisses on the balcony, but this time, Devlin is cooly beyond her reach and his sexual 'appetite' for her has noticeably cooled, after learning that she is to renew relations with a former suitor. He is visibly upset, tense and stern beneath his charming demeanor. Surprised by the rapid change in his mood, she asks what is wrong. He explains that her assignment is to reacquaint herself with Sebastian, part of the Nazi contingent. She is to exploit her sexuality and attractiveness like agent "Mata Hari" [Mata Hari was a famous, real-life Dutch spy used by the French during WWI to get information from German officers] to snare and "land" him - the target of US surveillance:

Alicia: What's the matter? Don't look so tense. Troubles? Well handsome, I think you'd better tell Mama what's going on. All this secrecy's going to ruin my little dinner. Come on, Mr. D., what is darkening your brow?
Devlin: After dinner.
Alicia: No, now! Look, I'll make it easy for you. The time has come when you must tell me that you have a wife and two adorable children and this madness between us can't go on any longer.
Devlin: I'll bet you've heard that line often enough.
Alicia: Right below the belt every time. Oh, that isn't fair, Dev.
Devlin: Skip it. We have other things to talk about. We've got a job.
Alicia: Oh. So there is a job.
Devlin: You, uh, you remember a man named Sebastian?
Alicia: Alex Sebastian?
Devlin: Yes.
Alicia: One of my father's friends, yes.
Devlin: He had quite a crush on you.
Alicia: I wasn't very responsive.
Devlin: Well, he's here. The head of a large German business concern.
Alicia: His family always had money.
Devlin: He's part of the combine that built up the German war machine and hopes to keep on going.
Alicia: Something big?
Devlin: It has all the earmarks of being something big. We have to contact him.
Alicia (after looking away and then walking away to sit down): Go on, let's have all of it.
Devlin: We're meeting him tomorrow. The rest is up to you. You've got to work on him and land him.
Alicia: Mata Hari. She makes love for the papers.
Devlin: There are no papers. You land him. (He walks behind her.) Find out what's going on inside his house, what the group around him is up to, and report to us.
Alicia: I suppose you knew about this pretty little job of mine all the time.
Devlin: No. I only just found out about it.

After relaying her assignment to her - to reacquaint herself with an old family friend and get "the papers" (or information), Alicia is hurt that he didn't turn down the assignment, or defend her character as a "new Miss Huberman" by arguing that she had changed - and was not the kind of "girl for such shenanigans." Acting distant, remote and inadequately supportive, Devlin leaves the decision up to her by failing to explicitly dissuade her. Not once does he re-affirm their love - instead, he covers up his cowardice and self-loathing with cruelty and indifference toward her:

Alicia: Did you say anything? I mean, that maybe I wasn't the girl for such shenanigans?
Devlin: I figured that was up to you - if you'd care to back out.
Alicia: I suppose you told them, 'Alicia Huberman would have this Sebastian eating out of her hand in a couple of weeks. She's good at that. Always was.'
Devlin: I didn't say anything.
Alicia: Not a word for that little love-sick lady you left an hour ago?
Devlin: (harshly) I told you, that's the assignment.
Alicia: Oh well now, don't get sore, Dev. I'm only fishing for a little bird-call from my dream man, one little remark, such as: 'How dare you gentlemen suggest that Alicia Huberman, (she stands) the new Miss Huberman, be submitted to so ugly a fate!'
Devlin: That's not funny. (He lights a cigarette.)
Alicia: Do you want me to take the job?
Devlin: You're answering for yourself.
Alicia: I am asking you.
Devlin: It's up to you.
Alicia: Not a peep, hm? Oh, darling. What you didn't tell them, tell me! That you believe I'm nice, and that I love you, and I'll never change back.
Devlin: (coldly) I'm waiting for your answer.
Alicia: What a little pal you are. Never believing me, hmm? Not a word of faith. Just down the drain with Alicia. That's where she belongs. Oh, Dev, Dev. (She goes inside, uncorks a bottle. Significantly, she takes a drink, framed behind the balcony window.) When do I go to work for Uncle Sam?
Devlin: Tomorrow morning.
Alicia (looking at their candlelight dinner setting on the balcony): Oh, we shouldn't have had this out here. It's all cold now. What are you looking for?
Devlin: I had a bottle of champagne. I must have left it somewhere.

Devlin forces her to compromise herself morally and simultaneously betrays her with his own romantic apathy and devotion to official duty. In spite of Devlin, Alicia agrees to the assignment - to form an amorous liaison with Alexander and marry him, a confederate of her father's, in order to complete the mission - and to gain access to the atomic secrets he is guarding.

On their way to meet Sebastian during his daily horse ride at a riding club, they glumly discuss their assumed identities. Their plan is to "accidentally" meet the spy on a riding trail. When they pass him on horseback the first time, Sebastian doesn't recognize her - and she is slightly disappointed. Then, she realizes that the brim of her fedora low on her brow had obscured her face. To provide another opportunity at recognition, Devlin jabs Alicia's horse with his foot to kick it into a galloping run. Sebastian gallantly catches up to her runaway horse. Their ploy is successful - Sebastian renews his relationship with her after saving her and becoming reacquainted. In the next scene, Devlin sits idly alone in an outdoor cafe while the woman he has fallen in love with has begun to prove her worthiness to her country by risking her life in a new affair.

Alicia and Sebastian meet again for their first dinner together in a fancy lounge. Sebastian complains about his work and state of boredom - "four years of dullness and disintegration." He attributes his youthful look to her presence. After noticing Prescott seated in a nearby room at a table, Sebastian informs her that Prescott is an "intelligence man." He also remarks: "He's rather handsome, isn't he?" (is he bisexual or empathetically placing himself in Alicia's position?). She describes her feelings about American agents: "I'm allergic to American agents. Their fine points don't particularly appeal to me." Speaking of her father's death, Sebastian encourages the renewal of her spirit: "Many things have died for all of us. We mustn't let our spirit die with them. Perhaps I can help you to forget. I'd like to." Alicia reveals her recharged feelings for him when he confesses his rekindled love and "hunger" for her:

Alicia: It's odd, but I feel at home with you.
Sebastian: You know my dear, I knew this was going to happen. I knew when we met the other day that if I saw you again, I'd feel what I used to for you. The same hunger. You're so lovely, my dear.

Alicia tells him that there is "no one" else, not even Devlin whom she says has "pestered me with his tenderness ever since I arrived...Mr. Devlin doesn't interest me." Alex invites Alicia to his home to meet his mother Mme. Sebastian at a small dinner party the following evening.