That evening in their apartment, Oliver and Irena worriedly discuss more of their marital problems and how they have drifted apart in their estranged marriage (a contrast to his easy rapport with Alice). Irena asserts her basic sense of truthfulness:

Oliver: People can love and people can still drift apart and that's what I feel is happening to us. We don't talk together openly. You're not frank with me.
Irena: I've never lied to you.

After further talk about how she won't seek psychiatric help any more, Oliver mistakenly mentions that he has again confided in Alice about her. To avoid inciting her jealousy and anger in a quarrel, he departs for the office to do some work, but decides at the last minute to first order some apple pie and a cup of coffee [real all-American food - he turns down an offer of chicken gumbo] at Sally Lunn's from black waitress Minnie (Theresa Harris).

Working late at the office (lit only by the light of a drafting table), Alice takes a phone call from an unidentified caller (Irena). Frustrated by the call, Alice speaks to the office's white cat: "John Paul Jones, don't you hate people who do that?" When the office cleaning lady mentions that Oliver just came by and went to a nearby restaurant, Alice decides to join Oliver. At Sally Lunn's, she immediately intuits that he is experiencing "stormy weather."

Suspicious of her husband having an affair after hearing Alice's voice on the phone at work, Irena spies on them from the street and discovers them seated together at a restaurant table. Their last few words of conversation imply that they are a couple to be reckoned with:

Oliver: Alice, you're very swell.
Alice: That's what makes me dangerous. I'm the new type of other woman.

As they leave the restaurant together, a chill sends shivers up Alice's spine, and she describes why - metaphorically and literally: "A cat just walked over my grave." Although Oliver eagerly offers to accompany her walk to her lodgings at the YWCA through Central Park (taking one of the concourses that cuts through the park from Fifth Avenue to Central Park West), she asserts her independence: "No thanks, I'm a big girl now and I'm not afraid."

The next scene is one of the two most famous stalking sequences within the film - a superb example of suggestive horror. As Alice walks alone at night through the park's underpass-transverse in shadowy streets along a stone wall, a scorned Irena follows after her in the darkness. The earliest views of the two women are full shots. Pools of light from the streetlights cast shadows at their feet, as the soundtrack accentuates their high-heeled shoes striking the pavement and presents close-ups of their strides. The pace quickens as Alice and her pursuer hurry more rapidly between the light areas (pools or circles of light under lampposts) and dark areas. All of a sudden, a discomforted Alice realizes that someone may be following her [a projection of her own guilt and fear of retribution?] - and she slowly turns to listen anxiously and view an empty street. What makes her most frightened and panicky is that the clicking of the footsteps behind her have abruptly ceased, but she senses that a forbidding presence still remains behind her. And then a low, panther-like growl and hissing sound (calculated to make the film audience jump from their seats) accompanies the jarring arrival of a city bus applying its air-brakes to stop at the curb - moving into the frame from right to left in front of her. She grabs the door handle to steady herself and turns around to watch disturbed, billowing tree branches adjacent to the top of the wall swaying and rustling back and forth. The bus driver (Charles Jordan) quips: "You look as if you'd seen a ghost." She gasps: "Did you see it?"

The bleatings of a flock of sheep signal that four of the helpless animals have been slaughtered and left on the ground - a park shepherd with a lantern inspects the dead carcasses and paw-prints of a large cat leading away. His light, in a tracking shot from left to right, illuminates the fact that panther paw-prints (silent) in the mud are transformed into high-heeled shoe-prints (their sound is resumed on the soundtrack).

Under a streetlight, Irena stumbles along as she clutches a handkerchief to her mouth. Her fur coat, looking like the hairy pelt of an animal, is disheveled and torn from the skirmish. She takes a taxi-cab home where a frantic Oliver again tries to make peace. Avoiding his touch and turning her back to him as he asks for forgiveness, she retreats to the bathroom in her bedroom. She runs the bath water and undresses, as a concerned Oliver begs to know her condition from outside her door. A close-up of the claw-foot of the antique bathtub prefaces a pan up to a hunched-over and weeping Irena in the tub, with her naked back and shoulders sprinkled by water droplets after she has washed away the blood. [She knows that she may be transformed into her monstrous and vicious cat personality under the right circumstances.]

In the film's one dream sequence, experienced by Irena as a nightmare, she is plagued by animated, art-deco black cats that emerge from the center of a spinning spiral. Fragments of Dr. Judd's earlier diagnosis ("there is in some cases a psychic need, a desire for death, to loose evil upon the world"), repeatedly heard on the soundtrack, are accompanied by the psychiatrist appearing in a diffused image to Irena as King John - the armored Christian knight with sword who rid Serbia of its evil cats. He draws and brandishes his sword - it gives way to a giant key - the one she saw in the panther's cage lock. [It represents her means to release evil, a black cat, upon the world.] The next day, Irena removes the key from the zoo cage's door as she witnesses the black panther, seemingly reading her mind while devouring a slab of meat.

In a clever transition, the panther from the zoo dissolves into a panther-like figurehead on a model of a warship in a museum's naval exhibit, where Irena, Oliver, and Alice are spending an afternoon. To brush Irena off, Oliver suggests that she go off on her own and look at "some beautiful moderns upstairs," but she objects to being an outsider: "But I like these little boats. I want to be with you. Don't send me away." Irena is exiled from their company when Alice and Oliver inspect a work-related "drawing of the Victory" - the last American man o'war. Feeling snubbed, Irena descends a staircase on her way out of the museum - where she pauses next to an ebony black Egyptian statue - a jackal-headed Anubis. After their museum visit, Alice and Oliver share a cab ride to the YWCA (where Alice resides and is dropped off). Irena follows behind her in a second cab.

The film's second famous tense stalking sequence begins when Alice asks the YWCA receptionist for a key to the basement pool area, while stroking a black kitten from a litter "of four." The black kitty trots after Alice toward the changing room area, as Irena arrives and slyly asks the receptionist: "Is Miss Moore in?" - she is directed toward the pool area. As Alice is about to turn off the locker room light, she notices that the black kitten is spooked by something on the stairway. A low growling noise and the sinister black shadow of an animal descending the stairs prove terrifying. Alice races toward the deserted pool and dives in. The shadowy play of the rippling wake of the wavy water appears on the indoor pool's claustrophobic walls, and more echoes of ferocious animal growls fill the air. Completely vulnerable, she treads water in the center of the pool as the walls alternately darken and lighten around her. The unnatural pattern and shadow of a prowling creature on the walls of the swimming pool obstructs the light - something is circling around her. The sounds of water drippings fill the void between louder snarlings. Suddenly, Alice screams for help with shrieking, distressed cries that bounce off the cavernous pool walls. The receptionist and a house maid speedily rush to the rescue - and find an amused Irena, calmly transformed from a panther, switching on the pool light. Alice claims to the staff that: "It was dark down here and Mrs. Reed coming in unexpectedly frightened me. I'm terribly sorry," yet she asks for them to not depart without her: "Don't go, I'm coming right out." Supposedly, Irena's excuse for trailing Alice was to find Oliver's whereabouts, although Alice nervously admits: "You'll probably find him at home." A footnote to the entire scene: the receptionist discovers that Alice's robe has been torn to shreds by vertical tracks of claws from a savage beast: "Gee whiz, honey, it's torn to ribbons."

Troubled by the pool incident, Alice phones Dr. Judd (off-camera) and summons him to the YWCA to tell him that she believes Irena's fears of lycanthropy. Irena was changed into a Cat Woman - twice: "How much do you believe about the cat people?" Fondling his phallic sword-stick/cane, Dr. Judd offers a rational explanation for the events: "I believe...exactly as I told Mrs. Reed. The story is a product of her own fear - her own overworked imagination." Alice, however, claims that Irena's version of the story may be more believable:

Alice: Twice, I've been followed by something that was not human, something that attempted to take my life. I believe that was the cat form of Irena.
Dr. Judd: Why should she wish to harm you?
Alice: Because I'm in love with her husband.
Dr. Judd: Oh, my dear Miss Moore, the story grows more and more charming, simpler too, all the time. You're both victims of fear. Mrs. Reed fears the past and you fear the present. Mrs. Reed has a very strong imagination and you have an equally strong conscience.

After displaying her torn robe, the lecherous and suave Dr. Judd is delighted by the prospect of counseling and speaking to Irena again - in person: "To understand this, I should first have to hear Mrs. Reed's version of the story myself. That should be a most interesting interview." Alice fears having him alone with the potentially-lethal woman:

Alice: I shouldn't advise you to see her alone.
Dr. Judd: Do you think I'm afraid of so charming a lady?
Alice: Dr. Judd, I know you don't believe me, but you must be careful.
Dr. Judd: You want me to carry some means of protection - a gun, perhaps, with a silver bullet? Is that what you mean?
Alice: If you're lucky enough to have one.
Dr. Judd: Hmmm. Of course, uh. (He displays the sword within his cane.) This isn't silver. (He snaps the sword back into its cane-sheath.)

Dr. Judd conducts another therapeutic session with Irena in his office - and initially confronts her with the fact of her untruthfulness. He continually fails to recognize Irena's problems and ultimately encourages their continuation. She denies his accusations, now claiming that she suffers from "lapses of memory" - although she is already aware of her transformative ability due to the curse. She also rebuffs the unethical doctor's sexual invitation - within their doctor-patient relationship - to kiss her and aggressively make an advance. In retaliation, he then expounds how she is on the verge of hallucinatory insanity:

Dr. Judd: You say you have lapses of memory for which you cannot account. They're becoming more frequent and you're afraid.
Irena: (begging) Help me.
Dr. Judd: I can't help you. You're not truthful with me.
Irena: (pleading) But I am. I've told you everything. I have not lied to you.
Dr. Judd: Do you sincerely believe that if your husband were to kiss you, you would change into a cat and rend him to bits?
Irena: I don't know. I'm only afraid.
Dr. Judd: (bending forward) And if I were to kiss you?
Irena: I only know that I-I should not like to be kissed by you.
Dr. Judd: (in a threatening tone) My dear Mrs. Reed. Sometimes in my profession there comes a contest of wills between the doctor and his patient. Patients are clever, very clever, and they can fool the doctor - sometimes. You're very clever and perhaps you enjoy this little game you're having with me, but I shall discover your secret.
Irena: (desperately) Dr. Judd, believe me, I beg you to believe me. I have no secret. I've told you everything. I have not lied to you. I need your help.
Dr. Judd: I can't help you, but I can warn you. These hallucinations approach insanity. This nonsense about Miss Moore, at the park and in the swimming pool. It's a deterioration of the mind, the escape into fantasy. And it's dangerous. (He brandishes his lit cigarette at her.) At this moment, I could go before a board and have you put away for observation. You're that close to real insanity. I can't help you. You can only help yourself. You keep going back to the mad legends of your birthplace. Forget them. You surround yourself with cat objects, pictures. Get rid of them. Lead a normal life.
Irena: You know, for the first time, you've really helped me.
Dr. Judd: Maybe it's because you interest me.

With new resolve to love her husband, Irena (with a cat brooch pinned to her right lapel) sets a candle-lit dinner table for Oliver and herself in front of a burning fireplace. She beams to him that she is now receptive to his advances and will be his true wife: "I went back to Dr. Judd's office. I'm no longer afraid." However, Oliver's solemn response that it is too late demonstrates how far their marriage has deteriorated:

Oliver: Believe me, Irena, I'd have been the happiest man in the world if you'd told me that a little while ago, but things have changed. I had to learn, maybe through this marriage of ours. I didn't want to tell you this, but now you see I have to. I love Alice. Irena, it's too late.
Irena: Too late. (She grasps her arms in front of herself and clenches her fist.)
Oliver: There seems only one decent thing for me to do. I'll give you a divorce. Believe me, it's better this way.
Irena: Better? Better for whom?...There's nothing you can say. There's only silence. (She crumbles and drops herself onto the sofa.) But I love silence, I love loneliness. (She whispers unintelligibly to herself.)
Oliver: Irena, you talk like an insane woman.

After she orders Oliver from the apartment for fear of attacking him, her sharp, clawlike fingernails angrily scratch and tear the fabric of her velvety sofa in three parallel, vertical lines.

In Sally Lunn's restaurant, over orders of "Bavarian cream," "Roquefort," and "apple pie," Dr. Judd plots conspiratorially with Oliver and Alice to have Irena committed. The treacherous doctor also sympathetically suggests to Oliver that he might like to annul his marriage to Irena first, since one can't divorce a person who's been declared legally insane. However, Oliver is determined to "take care of" his "unwell" wife, with Alice's supportive assent ("It's the only right thing, Ollie"):

I have pointed out two alternatives, Mr. Reed. Either have her put away for observation and restraint, or have your marriage annulled....As a psychiatrist, I should recommend that you have her put away. As your friend, however, I have much more reasonable advice to offer. I think you should have your marriage annulled. In that way, you are free of responsibility. You two could marry....The law is quite explicit, one cannot divorce an insane person...As you will. I'll have the commitment papers drawn up, and arrange an interview with Mrs. Reed at her apartment tonight.

But Irena doesn't appear for the six o'clock interview that evening, and the trio give up on waiting any longer after an hour and a half. Oliver turns off the record player (playing Irena's lullaby - thematic music derived from the traditional French lullaby Do, Do, Baby Do): "Let's not play that." As they all leave, Dr. Judd deliberately leaves his sword-cane ("walking stick") in their apartment - and deviously asks to borrow Oliver's key to return and get it. He purposefully leaves the apartment unlocked for his later use.

In the darkened drafting room during after-hours, Oliver and Alice catch up on some overdue work. She answers the phone - another silent hang-up call, and she quickly fears the premonition of threatening danger lurking nearby:

There was someone on the other end of the line. I could almost hear them listening. Then there was a little click as they hung up the receiver. That was the night I was followed on the transverse. Ollie, let's get out of here. I'm afraid. That was Irena. I know it was Irena who called. She could call from downstairs. She may be on her way up now.

Irena actually metamorphoses into a black panther in this drafting room stalking scene, slinks around in the dark beneath the furniture, growls, and threatens them in their locked-in office. The animal ignores Oliver's pleas: "Leave us, Irena!" Backed into a corner and underlit by the light of a drafting table, they protect themselves from being pounced upon by holding up a giant T-square as a crucifix (it casts the shadow of a cross on the wall) to ward off the evil creature: "In the name of God, leave us in peace." The object has the desired magical effect, and the bestial creature instantly disappears. They hurry from the office - and in the lobby where the revolving door turns, Alice recognizes Irena's lingering scent: "Irena's perfume: strong, sweet."

They telephone Dr. Judd, who has since returned to Oliver's apartment to await Irena's arrival. He is warned that Irena is "dangerous" but he refuses to believe that she is a fearsome threat. The psychiatrist hangs up on Alice when Irena steps through the door. The shifty, suave doctor stands close to Irena and purrs lovingly to her about keeping his appointment. His sexuality, not hers, becomes menacing when he proposes to kiss and ravish her:

You're late, aren't you? I kept my appointment. You see, I've never believed your story. I'm not afraid of you. I'll take you in my arms. So little, so soft, warm perfume in your hair, your body. Don't be afraid of me, Irena.

As the knight in armor with a sword-cane who believes he can tame the beast with a kiss, he precipitates her transformation into a black panther. She coldly accepts his forceful, predatory kiss without revealing any emotion in her blank face, but then the light dims. She takes on the dark cat's attributes - her face darkens and her eyes glint and sparkle, indicating that the mutation into a black panther is occurring. He draws back when she advances, terrified by the sight of her changing into a black panther. Dr. Judd grabs his sword-stick, knocking over a table lamp in the process. Giant shadows of the brutal struggle between the beast and the doctor are projected onto the walls and panther-screen by the downed light. The black cat leaps onto its prey as he vainly attempts to stab it with his protective, broken-in-half sword-cane - just as Oliver and Alice arrive and hear his horrendous screams of death from the foot of the staircase. As they rush upstairs toward the "racket" and plow through a curious group of onlooking neighbors, an unsteady Irena (holding her left shoulder wound) slips out of the apartment and hides in the shadows behind a potted plant to escape their notice.

She retreats to the foggy zoo and approaches toward the cage of the black panther. Irena unlocks the cage door with the stolen key to release the animal - and possibly to invite the creature to suicidally attack her. The animal growls and cowers back from her, but then leaps toward freedom. It strikes her, knocks her down with its powerful claws, and kills her with the blow. (After tumbling to the concrete, part of the broken sword-cane that has pierced her shoulder can be seen extending out of her back.) After she expires on the pavement, the panther vaults over the zoo's stone wall and is killed by a passing car (off-screen). Oliver and Alice race to the zoo where they find the open panther cage and the body of Irena lying nearby. The camera pans down to the non-descript (but feline) black figure, now still in death - Oliver kneels down to inspect it and speaks the film's final words to Alice:

She never lied to us.

The film is book-ended with another quotation in the end title - taken from John Donne's verse to emphasize the incompatible worlds that Irena inhabited:

But black sin hath betrayed to endless night
My world, both parts, and both parts must die.
Holy Sonnets, V. - John Donne.