Despite rejecting Oliver's love, when Irena grows wise to Alice's feelings, she stalks her three times, in the film's most memorable scenes. The first time is at night, in Central Park, and the sounds of high heels clicking, and shadows on the wall, and in the trees, is unnerving. Alice escapes when a bus pulls up, with a hissing sound. This is memorable, because she's looking to the left, the bus comes from the right. Its hiss sounds like a big cat's, which is what it would be in the hands of a lesser director than Tourneur, and which has, indeed, been copied hundreds of times since. The technique has become so popular that any time a film, in any genre, raises expectations, then dissipates with a subversion, the technique is called 'a bus.'

We then see a dead lamb at the zoo and cat prints that morph into high heels. One might wonder if Irena's clothes morph into a cat, as well. When she gets home, she freezes Oliver out of her room, and takes a bath, to cleanse herself of guilt, and possibly lamb's blood. The second stalking takes place in a pool, where Irena follows Alice at night, and where Alice's robe ends up ripped.

The final stalking is the least effective, dramatically and visually, for Irena stalks both Alice and Oliver at their office, and is warded off with a slide rule that looks like a crucifix, and Oliver's pleas to God. We also get to actually see a panther, which, given its relatively small size, decreases the fear factor, and makes the film a definitive supernatural thriller, whereas the earlier suggestiveness left the film open to being all in the minds of its characters. This manifestation of the supernatural element was forced upon Tourneur and Lewton by studio heads.

In the end, Oliver tells Irena he loves Alice and wants a divorce. Dr. Judd manipulates all the others so he can get Irena alone, and kisses her. Irena seems to welcome it, for she wants to assail him, and seemingly turns into a panther — again, which is shown, instead of just shadows. She mauls him in Oliver's and her apartment. Many of the scenes in this film were also obvious templates for the transformation scenes in Ken Russell's 1980 film Altered States. She then flees to the Central Park Zoo, and opens the panther cage — after having earlier stolen an absentminded zookeeper's key, which has obsessed her throughout the film — and the cat lunges at and mauls her. When Alice and Oliver arrive they find her dead, with part of Judd's cane sword in her. He laments that Irena, at least, never lied to them. It's hard to tell, from a distance, whether she is in human or cat form. The zoo panther, however, has been run over by a car in its escape.