The central 'twist' of "Persona" is not a single event but a gradual process: the complete psychological merger of Alma and Elisabet. Initially, Alma is the caregiver and Elisabet the patient. This dynamic reverses and then dissolves entirely. In a key scene, Elisabet's husband, Mr. Vogler, visits the cottage and mistakes Alma for his wife. Alma initially resists but then plays along, and Elisabet silently encourages this union, even placing Alma's hand on her husband's face. This confirms that the transference is mutual and complex.
Alma eventually confronts Elisabet, recounting the painful story of Elisabet's rejection of her own son, a story Alma could not possibly know in such detail. Bergman shoots the monologue twice: once focused on Elisabet's pained reaction, and a second time on Alma's face as she speaks the words with a cold, detached tone. This repetition suggests that both women are now one entity, sharing the same traumatic memory. The distinction between them has become meaningless.
The ending is famously ambiguous. After Alma forces Elisabet to say the word "nothing," we see Alma packing and leaving the cottage alone, as if Elisabet was never there or has been fully absorbed. The final shots return to the boy in the morgue and the film projector shutting down, breaking the fourth wall and suggesting the entire narrative may have been a cinematic construct, a dream, or a psychological exploration within a single mind. There is no resolution; the audience is left to question whether the women were ever truly separate individuals at all.