The newly-married couple are celebrating their post-marriage dinner in a Serbian restaurant, the Belgrade, on a snowy winter's night, with Oliver's work colleagues - the Balkan-like location was found and chosen by the all-American girl Alice. A premonition that something isn't quite right with Oliver's marriage to a foreign bride, after an off-screen civil ceremony, is mentioned by the Commodore - he speaks to Alice in an aside: "Oliver's bride seems to be a very nice girl, and a very pretty one too. Carver tells me she's a bit odd. She's worried about the marriage." Concealing her own unhappiness for having lost Oliver, Alice assures him that his worries are unfounded: "Nonsense, Irena's a grand girl. She and Oliver are going to be very happy together."

When the Commodore proposes a toast, an unnerving, knowing glance is cast back by a curious, cat-like woman (Elizabeth Russell) at the bar toward Irena - in one of the film's most unsettling and memorable scenes. The statuesque feline woman in a shimmering black dress has slanted eyes, a beguiling smile, and a black bow adorning the front of her hairdo that resembles tiny cat ears:

Commodore: To the bride! (They all drink a toast.) Look at that woman. Isn't she something?
Carver: (critically) Looks like a cat! (The cat-like woman rises.)
Irena: (to Alice) Thank you so much for this lovely party, Alice. I didn't know there was a Serbian restaurant.
Alice: Anything you want to know about this city, ask me. I know all the unimportant details.

The cat-like woman faces Irena and Alice, and addresses the terrified Irena in Serbian. [The voice of the cat-like woman, speaking only a few words, was dubbed by Simone Simon herself to create a sense of kinship!] After the psychic-kinship identification, Irena crosses herself to ward off the evil, pre-Christian influence. The fears and superstitions of her past have followed her to the 'jungle' of New York City. [Are there lesbian connotations in the greeting? or does the greeting simply convey that they are both accursed, bestial, dark Cat People with a Balkan heritage?]

Cat-Like Woman: Moia sestra. (Irena reacts in icy fear and doesn't answer.) Moia sestra? (Irena crosses herself. The woman leaves the restaurant. After a sigh of relief from everyone in the company, the party resumes.)
Alice: Well, how do you like that?
Oliver: (to Irena) What did that woman say to you, darling? (Irena doesn't answer.) What did she say? Now wait a minute, it can't be that serious. Just one single word.
Irena: (sobered) She greeted me. She called me sister. You saw her, Oliver. You saw what she looked like.
Oliver: (laughing) Oh, the cat people! She looks like a cat, so she must be one of the Cat People! One of King John's pets! (He playfully nudges Irena's chin with his right fist.) Oh, Irena, you crazy kid!

The couple are driven home to their now-shared apartment, and must endure listening to Carver's "corny" joke about weddings before being left alone:

Why would my wedding be a dollars and cents wedding?
- Because I haven't a dollar and the girl hasn't any sense.

Under a heavy snowfall with flakes that drop all over them, Irena begs an apology to Oliver for her virginal and frigid state and for not becoming a whole wife (an Americano "Mrs. Reed") for him. She acknowledges the presence of another foreign world of "evil" inside of her that prevents her from consummating her marriage:

Oliver: What is it, darling?
Irena: I'm going to beg...
Oliver: Mrs. Reed.
Irena: It's nice to hear that. Nice. I want to be Mrs. Reed.
Oliver: You are.
Irena: But I want to be Mrs. Reed, really. I want to be everything that name means to me. And I can't. I can't. Oliver, be kind, be patient. Let me have time. Time to get over that feeling there's something evil in me.
Oliver: Darling, you have all the time there is in the world if you want it. And all the patience and kindness there is in me.
Irena: Only a little time, Oliver, I don't want more than that.

Upstairs inside their apartment, they retire to separate rooms. Oliver knocks softly on her bedroom door to say good night - they are separated on their wedding night by her bedroom door. She crouches down by the inside of the door, desiring to claw on it, and wanting to grasp the handle to open it and make love to her new husband. But the nocturnal sound of the black panther-cat in the zoo prevents her from doing so and she withdraws her hand - it reminds her to remain caged inside, and she rests her head in resignation against the door. [A similar bedroom scene between an estranged couple - that also involves a cat - occurs in the final scene of the romantic comedy The Awful Truth (1937).] Unavailable for him, she responds with a very subdued good night. Sadly, the supremely-patient Oliver repeats an even-quieter "good night, Irena" and moves away from the door to sleep by himself on the couch on his wedding night.

The next scene opens almost a month later at the zoo outside the panther's cage, where Irena often visits and watches the beautiful panther. The quaint zookeeper/attendant (Alec Craig) [who often sings Bernard Herrmann's song "Nothing Else to Do" from All That Money Can Buy (1941)] snorts that "Nobody comes to see him when they're happy...the monkey house and the aviary gets all the happy customers...He ain't beautiful. He's an evil critter, Ma'am." He sets an ominous tone by quoting from the Book of Revelation in the Bible, after the black animal hisses (in closeup):

Where the book's talking about the worst beast of 'em all. It says, 'and the Beast which I saw was like unto a leopard'...Like a leopard, but not a leopard. I guess that fits this feller.

While sketching at home (a drawing of a woman that resembles the black-gowned Cat Woman in the restaurant), Irena playfully extends her hand to pet her canary in its cage. The bird struggles to escape from her grasp and then falls dead to the bottom of the cage. She removes the poor lifeless bird, places it in a small box, takes it to the zoo, and deftly tosses the feathered gift toward the panther for food.

That evening, Irena tells Oliver that she envies every other women "on the street" who "lead normal happy lives" and "make their husbands happy." When she explains that the bird literally "died of fright," he downplays the incident: "That's nothing. I had a rabbit once that hated me, yet I grew up to be quite a nice fella." He grows more concerned when she describes that she was compelled at "the panther's cage...to open the box" and throw the bird at the animal:

Oliver: Irena, I've been trying to kid you out of it. Maybe that's wrong...I've tried to make you realize all these stories that worry you are so much nonsense, but now I see it's not the stories. It's the fact that you believe them. We've got to have help, Irena. (She glances at the statue of the knight impaling the cat.) Not that sort of help, there's something wrong and we have to face it in an intelligent way. We don't need a King John with fire and sword, we need someone who can find the reason for your belief and cure it. That's what we need - a psychiatrist.
Irena: Find one for me, Oliver, the best one, the very best one.

After her urging, Irena undergoes hypnosis treatment in the office of Dr. Louis Judd (Tom Conway, younger brother of actor George Sanders) in the next scene. [He is the author of The Anatomy of Atavism from which a quote was taken at the film's start.] She is reclining back on the doctor's couch with her eyes closed - with a bright moon-like spotlight framed on her face, while the psychiatrist sits to her right and prompts her: "You were saying the cats...?" She responds that she is tormented by the cats' hereditary, supernatural curse - her periodic changes into a panther:

(they) torment me. I wake in the night and the tread of their feet whispers in my brain. I have no peace, for they are in me.

When the session ends, he floods the room with light by opening up the curtains and then he switches off the spotlight. He remarks that "hypnosis always tires me," but that he has taken notes of her fantastic answers to his questions. She feels embarrassed and "ashamed" for having revealed "childish" ideas. He ridicules her primitive fears and refuses to believe them. He explains that she is being victimized by childhood trauma, her own beliefs and her paranoia about an ancient homeland curse or magical spell that will metamorphosize her into a passionate, animalistic killer if she is emotionally aroused:

I have it all here. Most interesting. You told me of your village and the people and their strange beliefs...and the Cat Women of your village too. You told me of them. Women who in jealousy or anger or out of their own corrupt passions can change into great cats like panthers. And if one of these women were to fall in love, and uh, if her lover were to kiss her and take her into his embrace, she would be driven by her own evil to kill him. That's what you believe and fear, isn't it? (Irena nods.) These things are very simple to psychiatrists. You told me about your childhood, perhaps we'll find this trouble stems from some early experience. You said you didn't know your father, that he died in some mysterious accident in the forest before your birth, and because of that the children teased you and called your mother a witch - a Cat Woman. These childhood tragedies are inclined to corrode the soul, to leave a canker in the mind. But we'll try to repair the damage. You're not to worry.

[One may further interpret the story by filling in between the lines. In the forest, Irena's father made love to Irena's mother and impregnated her. During the passionate act of intercourse, she was transformed into a homicidal panther - a Cat Beast/Woman - and she murdered Irena's father (the "mysterious accident").] When she asks the doctor about what she should tell her husband, the self-interested Dr. Judd reveals his obvious personal desire for her by advising: "One tells him nothing."

Upon her return to her apartment, Irena finds Alice sharing a cigarette with her husband under a cloud of smoke - one that has quickly dispelled the perfumed smell of Lalage. She also learns, to her amazement, that Alice recommended the 'hand-kissing' Dr. Judd ("I guess he knows all there is to know about psychiatry") and that Oliver has already told Alice all about their intimate marital problems ("Alice knows, darling"). After Alice is shown to the door, leaving an offended Irena, the young wife - with a growing sense of jealousy (from a suggestion planted by Dr. Judd) - chastises her husband for confiding in his female work colleague:

Irena: How can you discuss such things, such intimate things about me? How much did you tell her?
Oliver: Oh, you can tell Alice anything, she's such a good egg - she can understand anything.
Irena: There are some things a woman doesn't want other women to understand.

Irena retreats to her bedroom, and then later awakens in the middle of the night for a nocturnal visit to the panther's cage in the zoo. She wears a black fur coat over her ankle-length dress, similar to the costume worn by the Cat Woman. After her return to the apartment, she tells Oliver a half-truth about her absence ("I just walked"). With a quavering voice, he apologizes for the previous afternoon. When she cautions him about inciting her sexual jealousy or anger [the dominant plot theme of female rivalry continues for the remainder of the film], he contritely promises to keep her happy:

Irena: Oliver, we should never quarrel, never let me feel jealousy or anger. Whatever is in me is held in, is kept harmless, when I'm happy.
Oliver: I'll turn handsprings, darling. I'll dance in the streets to make you happy.

At work the next day, Oliver absent-mindedly makes a third miscalculation during their ship-design work ("I'm getting careless in my old age"), causing Alice to suggest that they take a cigarette break together at the water cooler. She correctly suspects that something is wrong with his marriage: "Must be marriage." He confides more of his agony over Irena's condition and seeks solace from Alice. His wife has avoided all her appointments with Dr. Judd since her first visit, and it is beginning to take its toll on his suddenly unhappy life. Seizing the opportune moment, the down-to-earth Alice forthrightly admits her love and caring for Oliver, even though he's a married man. Although "Americano" Oliver is entranced and hypnotically fascinated by Irena's exotic and mysterious appearance, he confides that he doesn't really know her. She is demonized for her emotional, dark troubles stemming from her European roots:

Oliver: You know, it's a funny thing, I've never been unhappy before. Things have always gone swell for me. I had a grand time as a kid, lots of fun at school, here at the office with you and the Commodore and Doc. That's why I don't know what to do about all this, I've just never been unhappy...
Alice (unable to hide her sniffles): I can't help it. I just can't help it. I can't bear to see you unhappy. I love you too darn much, and I don't care if you do know it, Ollie. I love you. I'm sorry, forget it. There's Irena - you're in love with her.
Oliver: I don't know. All this trouble has made me think, I don't know what love really is. I don't know even whether I'm in love with Irena.
Alice: I know what love is. It's understanding. It's you and me and let the rest of the world go by. It's just the two of us living our lives together, happily and proudly. No self-torture and no doubt. It's enduring and it's everlasting. Nothing can change it. Nothing can change us, Ollie. That's what I think love is.
Oliver: Well, that's not the way I feel about Irena. It's a different feeling. I'm drawn to her. There's a warmth from her that pulls at me. I have to watch her when she's in the room. I have to touch her when she's near. But I don't really know her. In many ways, we're strangers.
Alice: You and I - (she grasps his hand) - we'll never be strangers.

Back at the zoo, Irena realizes that the zoo attendant has forgetfully left his key in the cage's lock - and she thoughtfully returns it to him, but he isn't very worried: "Nobody'd want to steal one of them critters." Dr. Judd, who has predicted where she might loiter ("You told me many things") and observed (unseen) the key incident, steps forward and compliments Irena: "You resist temptation admirably." He explains further why she might have wanted to keep the key - for suicidal intentions [a foreshadowing of the film's climax]:

There is in some cases a psychic need to loose evil upon the world, and all of us carry within us a desire for death. You fear the panther, yet you're drawn to him, again and again. Couldn't you turn to him as an instrument of death?

He is concerned that she has been avoiding other appointments. She explains that his insistence upon ascribing her fears to her mental state are inadequate, because the roots of her problems rest in her inner soul:

Irena: I don't feel you can help me. You're very wise, you know a great deal, yet when you speak of the soul, you mean the mind, and it is not my mind that is troubled.
Dr. Judd: What a clever girl, all the psychologists have tried for years to find that subtle difference between mind and soul - and you've found it.
Irena: It does seem presumptuous of me, doesn't it? Goodbye, doctor.