Trama

A government agent recovering from a nervous breakdown deciphers a death threat written in ancient Hebrew.

When his wife is killed in a restaurant shoot-out, intelligence man Harry Hannan (Roy Scheider) has a breakdown and finds that his department doesn't want him back. Someone's trying to kill him and it could be them, though a cryptic Jewish death-threat suggests there's something else going on. His only ally seems to be mousy Ellie Fabian (Janet Margolin) who has managed to move into his New York apartment.—Jeremy Perkins {J-26}

The film opens in a Mexican cantina across the border from El Paso, where government agent Harry Hannan (Roy Scheider) is canoodling with his wife Dorothy (Sandy McLeod). Harry spots an informant (Bert Santos) that he was supposed to meet in a few days. Realizing he is about to be attacked, he shoves his wife to the ground and starts shooting at the informant's two companions (Joe Spinell and Jim McBride) who return fire and flee the restaurant. Harry's wife dies in the attack, and he suffers a nervous breakdown. He spends 161 days in a Connecticut sanitarium before being released.

While waiting at a Hudson River train station on his way back to his home in New York City, Harry stumbles and nearly falls into the path of an express train. He goes to the makeup counter at Macy's to retrieve his next assignment. The saleswoman gives him a lipstick shade called "Sunset Rose", but when he disassembles the applicator, the assignment slip inside is blank. He accosts his contact who assures him that the agency probably just does not have any work for him at the moment.

When Harry returns to his apartment, he finds it is occupied by a doctoral student named Ellie Fabian (Janet Margolin). She explains that she had a perfectly legal sublet arranged while she is in the last semester of her studies at Princeton. Ellie claims that the housing office said the Hannans would be gone indefinitely. She gives Harry a note that was slipped under the door, but it contains only a few Hebrew characters that Harry cannot read.

Paranoid that he is being targeted by his own agency, Harry visits his supervisor Eckart (Christopher Walken), who assures Harry that the agency has higher priorities. Eckart insists that Harry is not ready to return to the field, but that he is perfectly safe. After their conversation, Harry notices that he is being surveyed. He loses the tail and rushes to the American Museum of Natural History, where Ellie is carbon dating a skull. She is astonished that he found her, but he rattles off facts about her life, including that she is conducting a study of prostitution.

He gleaned everything from his brief encounter with Ellie in his apartment. He gives her some money and urges her to stay in a hotel, because he fears she will be accidentally targeted by whomever is after him. Ellie stays in the apartment despite Harry's request. When Harry wakes from a nightmare, he tells Ellie about the death of his wife. He takes a prescription pill, but immediately spits out, realizing that it is cyanide.

Harry takes the Hebrew note to a local rabbi (Lou Gilbert) who can only partially decode it. The rabbi informs the agency that Harry has visited him, and Eckhart orders Harry's murder. Ellie suggests that they take it to her friend at Princeton who specializes in Hebrew studies. On the train, Ellie tells Harry about her grandmother, and confesses that she inherited her wild streak. Harry notices an old man looking at him, and the camera reveals that another agent is also on the train.

At Princeton, Ellie introduces Harry to Richard Peabody (John Glover), who is very possessive of Ellie. He decodes the note for Harry and explains that it means "Avenger of Blood." Peabody has accumulated several of the notes over the years, and they were all attached to very peculiar murders. Harry is the first one to have received the note and lived.

The next day, Harry is lured to a trap by the other agent. He manages to kill the agent during a shootout in a bell tower. There, he encounters the old man from the train, Sam Urdeil (Sam Levene). Sam explains that he is part of a committee investigating the blood murders. Together, they investigate the various clues, and they piece together that Harry's grandfather owned a brothel on the Lower East Side of Manhattan.

Meanwhile, in Niagara Falls, Ellie is seen putting on makeup at a vanity. She is dressed as a prostitute, and she lures a married man into a bathtub with her. As she has sex with him, she drowns him.

As Harry and Sam put together all their information, they are lead back to Princeton. Harry realizes that Ellie is the one murdering men, on behalf of victims of white slavery like her grandmother. He drives her up to Niagara Falls, where they have an emotional confrontation. She tries to kill him but confesses that she loves him. He is conflicted, but he tells her that he will turn her in. Ellie runs from him, and the film ends with a prolonged chase through the hydroelectric power plant. It ends above the falls, where Harry grabs Ellie, but she struggles and ends up plunging to her death.