Time Signatures

Frequency is a 2000 film that contains elements of the time travel, thriller, and alternate history film genres. It was directed by Gregory Hoblit and written by Toby Emmerich. The film stars Dennis Quaid and James Caviezel as father and son, Frank and John Sullivan respectively. It was filmed in Toronto and New York City. The film gained mostly favorable reviews following its release and was released in DVD format on October 31, 2000

Plot
The film is set in New York City during October 1999. John Sullivan (Caviezel), a 36 year old homicide detective, is still traumatized over the death of his fireman father, Frank Sullivan (Quaid), thirty years ago. Living in the same house where he grew up, he discovers his father’s ham radio following a breakup with his girlfriend and begins transmitting.

Due to unusual aurora borealis activity, John discovers he has managed to make contact with his father exactly 30 years in the past shortly before the date of the warehouse fire that will kill Frank. John is able to warn his father of the fire that would have otherwise taken his life, and although Frank initially disbelieves that John is his future son, he heeds John’s advice when he realizes that John accurately described the outcome of Game 2 of the 1969 World Series.

Having saved his father from the fire, John creates a new timeline, while paradoxically retaining his memory of the old. In this altered timeline, Frank instead dies of lung cancer due to his chain-smoking, and John’s mother Julia “Jules” Sullivan (Elizabeth Mitchell) is murdered by a serial killer. In the old timeline John’s mother left her job as a nurse at a hospital to attend to Frank’s funeral arrangements. In the new timeline, she remains at work and is present to save the life of a man who is later revealed to be the “Nightingale killer”, a man who would have died that night due to being given a mix of Benazepril and Benadryl had she not been there to save him. The “Nightingale killer”, in the erased timeline, had killed only three nurses before his death, the corpse of one of the victims not being discovered until 1999. Having been saved from death, he goes on to kill a total of ten women; his sixth victim is Julia.

Using information from 1999 police files on the impending seven killings, John and Frank work together across the gap of time to stop the murderer in 1969 and save Julia. Frank successfully averts the murder of the first expected victim, but when he tries to prevent the next, he is attacked by the killer in a nightclub bathroom and his driver’s license is taken from his wallet. When he regains consciousness, Frank rushes to the woman’s apartment only to find he is too late.

John realizes the Nightingale killer’s fingerprints are now on Frank’s wallet. John tells his father to empty and hide that wallet in the house where it will remain untouched for 30 years. Once Frank accomplishes this, it suddenly appears in 1999 in the same spot. John takes the wallet to the crime lab and learns that the fingerprints belong to a now-retired detective named Jack Shepard (Shawn Doyle). However, with his driver’s license having been planted at the latest murder scene by the killer, Frank becomes a suspect of the murders and is taken in for questioning by his police detective friend (and John’s later boss), Satch DeLeon (Andre Braugher).

At the station, Frank is confronted by Shepard, but Frank subdues him and escapes the station. Later searching for evidence in Shepard’s apartment, Frank is caught in the act by Shepard and chased to a stockyard. With Satch convinced of Frank’s story by his accurate prediction of the outcome of the World Series, Satch discovers Shepard’s guilt and Frank is cleared of all suspicion after a fight in which Shepard is presumed dead. However, John knows this cannot be true because his 1999 family photo still shows his mother absent: she was still murdered.

That night, while the two are talking on the radio, Shepard suddenly breaks into the Sullivan household, both in 1969 and 1999. Just as Shepard is strangling John in 1999, Frank gets a shotgun and blows off the killer’s hand in 1969. In 1999, Shepard’s hand suddenly shrivels and vanishes before his eyes; the house suddenly changes as if someone else lived there. Out from the shadows comes the living Frank, who shoots Shepard again, killing him. In this final timeline, Frank neither died in the warehouse fire, nor from lung cancer, having quit smoking at his son’s request.

The film concludes with a neighborhood baseball game in 1999. Frank and Julia are there, along with John, his wife (the girlfriend who had left him in the original timeline) and his son, Frank Jr..

from wikipedia