The Girl Who Knew Too Much

Nora Davis arrives in Rome to visit her aging aunt. On the first night, the aunt dies, prompting Nora to head to a nearby hospital to notify Dr. Marcello Bassi.

On her way to the hospital, Nora is mugged and knocked unconscious in Piazza di Spagna. The assault leaves her briefly incapacitated as she struggles to comprehend what is happening.

When Nora regains consciousness, she witnesses a young woman being murdered in front of a house and sees a bearded man pulling a knife from the corpse. She faints again, unable to process the horror of what she just saw.

The next morning in the hospital, Nora reports the incident to the police, but they do not believe her due to a lack of physical evidence. The authorities offer little help, leaving her frustrated and isolated.

At her aunt's funeral, Nora meets Laura Craven-Torrani, a close friend who lives in Piazza di Spagna. Laura invites Nora to stay at her house in Rome before she leaves for Switzerland the next day.

Nora reads newspaper clippings about the Alphabet Killer, a serial killer who murders victims in alphabetical order by surname. The latest victim is revealed to be Laura's sister, killed ten years earlier in front of Laura's house.

Nora receives a telephone call taunting her by saying that 'D' is for death. The chilling message deepens her fear of a looming danger connected to the case.

Marcello takes Nora on a sightseeing tour of Rome to distract her from recent events, and their professional relationship begins to deepen into a romance.

That night, after Marcello drops Nora off at the Craven house, an anonymous call lures her into an empty apartment. Marcello follows, and they discover the apartment is leased to investigative reporter Andrea Landini, who has been secretly following them.

Nora and Marcello confront Landini, who explains that he worked with the police on the Alphabet Murders and was dismissed when the case stalled. He admits he has been following them and claims to want to prove Straccianeve's innocence.

Nora agrees to help Landini, but their investigations across Rome fail to uncover solid clues. The hunt for the killer stalls as they chase wrong leads.

Nora visits Landini's apartment and finds evidence pointing to Landini, including a tape recorder, a confession note on his typewriter, and a photo of Nora labeled as a potential fourth victim. She soon discovers Landini dead in the apartment, an apparent suicide.

Nora learns from the morgue that the young woman's body is Straccianeve's daughter. The revelation shifts the investigation and raises new questions about who is responsible.

Alone in the Craven house, Nora encounters a deranged Laura who confesses to multiple killings: she murdered her sister for inheritance and stabbed her husband to keep him from having her committed. Her husband, dying, also shoots Laura in self-defense, ending Laura's rampage.

Nora survives the night and is reunited with Marcello, who supports her through the ordeal. They plan to marry soon, looking toward a hopeful future together.