After a night of revelry on New Year’s Eve in New York City, Bernadette Flynn and her friend, Allison Hawkins, share a cab and part ways. Back in her apartment, an intoxicated Allison is attacked and murdered. Bernadette’s father, Mayor Eamon Flynn, is upset that a serial killer is loose, and tells police commissioner Frank Starkey to reinstate his disgraced brother, Nick Starkey, who now works as a fireman. Frank arrives at a three-alarm fire in time to see his brother jump from a burning building, carrying a girl in his arms. Nick does not want to return as a detective but Frank confesses that his job is on the line, and Nick agrees to help. Later, the mayor tells Frank the strategy for the press conference, where he will announce Nick’s return to the police force. Frank is worried about his public image: if Nick catches the killer, Frank will look bad for previously firing him, but he will also be held accountable if Nick should fail. Captain Vincent Alcoa interrupts the meeting to protest Nick’s return, but the mayor insists that Nick be given full authority. Later, Flynn learns that Nick has agreed to work on the case on condition that he cook dinner for Frank’s wife, Christine. The two were once married. Christine snoops among Nick’s bookshelves and discovers several photographs Nick saved of their happy married life. While Christine complains about the meal, Nick confesses that he is still angry about their divorce, and his brother Frank's betrayal. When he inquires if she misses him, too, Christine claims she is happy in her new marriage. Nick accuses her of marrying Frank for his money, prompting Christine to slap his face and leave. The next day, Nick removes the furniture from his new office. He demands that Capt. Alcoa hire his artist friend, Ed, as his assistant, and requires that he buy an expensive computer. The captain grudgingly complies. After the funeral of heiress Allison Hawkins, Nick follows Bernadette Flynn to an outdoor skating rink in Central Park and seduces her. After making love, they walk to Allison Hawkins’s apartment and look for clues. Bernadette admits she is scared to go home, believing she could also be a target. Nick offers to let her stay at his apartment while he works late at the station. As Ed escorts her away, Nick examines several case files. The next day, he tells Frank that the killer was angry toward women, but Frank is not impressed with Nick’s theory of the motive. Back at Nick’s apartment, Christine appears at the door with a bottle of wine. She is disappointed that Nick is not at home, and gives Bernadette the bottle. At the office, Nick sees a pattern in the dates of the previous murders that is based on prime numbers, and determines the killer will strike again on January 5th. However, Capt. Alcoa refuses to give Nick the resources that he needs to prevent the attack, and another murder takes place. A killer jumps out the window of his victim’s high-rise apartment, and his body is trapped in an awning. Although the mayor and the police commissioner are convinced the dead man is the serial killer, Nick is skeptical, and asks to look at the victim’s apartment. The next day, he declares that the killer is still at large, but Capt. Alcoa closes the case. Nick insists on twelve more hours to solve the mystery, and then promises to transfer back to the fire department. Nick looks at an aerial view of the buildings, where the killer targeted his victims, and realizes the locations resemble the constellation Virgo. If Nick can determine the placement of the missing star, he will know where the killer will strike next. Nick also notices that the floors, where the previous crimes were committed, form a pattern that resembles musical notes of the song “Calendar Girl.” He fills in the last note of the song, which determines the floor where the killer will appear next. With Bernadette and Ed, Nick sets up a stakeout in a utility room diagonally across from the apartment where he suspects the next attack will take place. When the killer picks the lock on the front door, Nick and Ed ambush the female apartment owner, hiding her in the utility room. Nick waves his police badge and explains that Bernadette is going to take her place so they can catch the killer. Bernadette places a protective collar underneath her turtleneck to protect her from strangulation and enters the apartment. When the killer attacks, Nick has difficulty breaking the door with a sledgehammer, but just barely saves her in time. As Nick announces the suspect is under arrest, the assailant dashes past the detective and disappears down the hallway. While Nick wrestles with the killer on a staircase, Bernadette telephones the station for backup. Capt. Alcoa orders his men to the scene. Meanwhile, Christine is at the station and happens to see the building address. She arrives and just as her husband, Frank, and other officers draw their guns. Nick emerges from the building carrying the killer rolled up in a section of carpet. As he deposits the carpet on the ground, it unravels, and the suspect is revealed. Nick collapses, requesting a cup of espresso, and Christine walks over and announces she has left Frank. However, Nick is no longer interested in reconciliation, and she wishes him good luck. With Bernadette by his side, Nick announces his desire to cook her haggis for dinner once he recovers from his injuries. Upon hearing the description of the Scottish dish, she remarks that it sounds unusual but she is willing to give it a try.