The Bird with the Crystal Plumage

Sam Dalmas witnesses Monica Ranieri being attacked in a Rome art gallery by a man in a black raincoat. He tries to intervene but is trapped between the sliding glass doors as the assailant escapes. Monica survives the assault, and Sam becomes a key witness to the case.

The police confiscate Sam's passport to prevent him from leaving Italy, effectively binding him to the investigation. Sam resolves to help Inspector Morosini uncover the truth behind the night’s events and locate the killer.

Sam visits the antique shop where the first victim worked and discovers the last item sold was a painting showing a man in a raincoat stabbing a woman in a snowy landscape. The painting hints at a recurring motif and a possible link to the earlier attack.

The killer phones Sam at his apartment and threatens to kill Julia unless he abandons his investigation; he records the call, creating a crucial evidentiary lead. Sam realizes the killer is watching him.

Sam travels to a nearby town under the pretense of buying a painting; the artist explains the painting is inspired by an actual attack that occurred ten years earlier. The artist’s remarks confirm a real case behind the artwork, intensifying the investigation.

Back in Rome, the killer makes another attempt on Julia while she is alone in Sam's apartment, but Sam returns in time to save her. The killer escapes before he can be captured.

Police isolate an odd cricket-like noise in the recording of the phone threat, which Carlo identifies as the call of a rare South Caucasus bird—the bird with the crystal plumage. The bird’s only specimen in Italy is kept at a zoo in Rome, linking the clue to a concrete location.

Sam, Julia, Carlo and the police travel to the Rome Zoo, where they piece together how the killer’s scheme aligns with the bird clue. Sam observes that the Ranieri apartment overlooks the bird’s cage, tying the case to Monica.

In the Ranieri apartment, Monica and Alberto struggle over a knife; Alberto falls from a window and dies, confessing to all the murders. The revelation confirms the killer’s identity and motive, unmasking Monica as the perpetrator in the end.

Sam discovers that Julia has vanished and tracks her to a dark apartment; he finds Carlo dead and Julia bound, while Monica, in a black raincoat, taunts him. He quickly realizes Monica is the killer and pursues her through the city toward the art gallery.

Monica flees to the art gallery; Sam follows her inside as sirens approach. She drags a heavy spiked sculpture and knocks Sam to the floor, escalating the confrontation.

Police burst in and arrest Monica after she is subdued with the spike; Sam is freed from danger. Monica is then taken away to a psychiatric hospital for treatment.

A television interview with a psychiatrist reveals Monica was a trauma victim ten years earlier; seeing the painting triggered her mania and she identified with the attacker. Alberto also suffered an induced psychosis that helped cover up the murders.

Sam and Julia are reunited and fly back to the United States, leaving Rome behind. The couple begins a new chapter away from the nightmare they endured.