This film is kind of a cross between BACK TO THE FUTURE and FIELD OF DREAMS.
We're going to do a lot of jumping around here so you may want to take notes...

Dennis Quaid plays Frank Sullivan, a fireman in 1969 with a wife and 6 year old son John. Frank loves the Mets and they are just about to begin the 1969 World Series. They live in New York and the town is being terrorized by the Nightingale Killer, who has already killed 3 nurses.

Jim Caviezel plays John, 30 years later in 1999. His life is in turmoil, never having gotten over his dad's death in a warehouse fire in 1969. His girlfriend has left him, he still calls his mom every night and he lives in the house he grew up in.

One night, he discovers his dad's old ham radio while looking for fishing gear in the closet. He plugs it in and after a few tries, hears some guy named Frank on the other end. After a couple days of this they realize that they are father and son, 30 years apart and are talking off "the mother of all sun spots." John tells his dad not to follow his instincts and to go the other way in the fire that will happen later that day. To prove he's right, he also tells him the outcome of game 1 of the series.

Frank thinks he's nuts but when the game turns out just as John had said and he finds himself trapped in a burning warehouse, he goes the other way and is saved.

Now any of you that have seen BACK TO THE FUTURE know that when you change the past, it directly effects the present.

All of John's friends know that his dad died of lung cancer 10 years ago, not in a fire. Every paper from his scrapbook now shows Frank as the hero of the warehouse fire, not as a casualty of it. Suddenly, John's mom is no longer around. She was murdered in 1969 by the Nightingale killer, and his body count now is up to 9, including his mother.

Turns out that since Frank never died, she never had to leave the hospital that night and was then fair game for the killer.

John is now a detective working on the Nightingale case. He tells Frank which nurses are going to be killed, when and how. Frank sets out one by one, to prevent it. The killer attacks Frank in a bathroom taking his ID out of his wallet so he knows where he lives. Frank goes to the house of that nights victim but is too late. Now he is a suspect since he was seen at her house.

Since the killer touched Frank's wallet, John has a plan to take Frank's wallet and hide it in the house. When Frank does this, it suddenly appears 30 years later in the same spot. John takes the wallet to the crime lab and discovers that the fingerprints belong to a now retired detective. John confronts the killer in 1999 at the same time that Frank confronts him in 1969. Frank thinks he killed him but he actually got away. John knows his dad didn't kill him since John's family photo's show his mom missing. She was once in them but disappeared from the photos' once Frank didn't die in the fire.

That night while the two are talking on the radio, John convinces Frank to quit smoking. The killer breaks into the house, both in 1969 and 1999. Just as the killer is strangling John in 1999, Frank gets a gun in 1969 and blows off the killers hand. The 1969 killer runs out of the house. The 1999 killer now with one hand missing, is just about to attack again when all of a sudden everything in the room starts changing, as if someone else lived there. Suddenly out of nowhere the 1999 killer is blown away from someone in the other room. Out from around the corner comes Frank, now an old man. He never died in the fire or from lung cancer thanks to John.

The film ends with a neighborhood baseball game in 1999 with all their friends and coworkers. Old Frank is playing in the game with John while John's mom and his wife (the girlfriend that left him) and kid are watching. His buddy (which he earlier in the film told him as 1999 John to 1969 buddy, to remember one word... Yahoo) is now driving a Mercedes thanks to Yahoo stock.

Spoiled by: The Movie Spoiler