"Frequency" is the latest in that long and often honorable line of unforeseen-consequences-of-time-travel stories, the ones that used to be a mainstay of early sci-fi magazines, where the pin dropped by mistake years before changes all life on the planet into a) a fascist dictatorship, or b) an agrarian paradise, and the hero's task is to reinvent history so that everything comes out all right again.

Here it isn't the pin that dropped but a conflation of sunspots and the aurora borealis, that supposedly happened in New York in October 1969, in the middle of the world series between the Mets and the Orioles, and again in 1999. It seems that in 1969, New York City fireman Frank Sullivan (Dennis Quaid, with the kind of ersatz Queens accent that only a Hollywood voice coach could produce) died in a warehouse fire, leaving his wife, nurse Julia (Elizabeth Mitchell) and 6-year-old son John (Jim Caviezel). But thirty years later, in 1999, the sunspots encourage John, who grew up to be a city detective and still lives in the old house, to haul out his dad's old ham radio, and guess what -- he reconnects with his dad, who's back in 1969, just a day before the fire.

Now it happens that young John, who read the news stories of his father's death, learned that if Frank had chosen another route out of the burning warehouse he would have survived. So via ham radio he tells his dad this, and, uh-oh, history is changed forever, because when that alarm comes Dad chooses the new escape route and lives to tell the tale. But does he? He's not around now, thirty years later. What did happen to him?

And there's more. It seems there was a serial killer at work back then, murdering nurses in what the tabloids called the 'Nightingale murders.' And one of those he targeted was, guess who, nurse Julia. And if father and son, working together across the time warp, don't find the killer before he gets to Julia, and before the aurora dies down again, God only knows what kind of reality we'll end up with.

So this is a kind of Chinese-box story, where there are levels within levels, and each one changes reality. In fact, in the family photo that John keeps on his desk, the figures in it keep popping in and out of frame as each action changes every subsequent action. People seem to live and die and live again every five minutes, according to what the son and father are doing to solve the serial killings.

The whole thing has actually been reasonably well thought out by writer Toby Emmerich and director Gregory Hoblit, and probably has perfect internal logic, though you couldn't prove it by me, since I got lost somewhere in the fourth or fifth of the alternate-reality plots, which also call for overcoming skepticism by elder police supervisor Satch (Andre Braugher) who can only be convinced by the uncanny predictions, made by Jim in the future, of what's going to happen in each of the 1969 series games.

The performances are an odd mixture, with Quaid relentlessly manic throughout and Caviezel just as relentlessly depressed. There are a couple of nicely inserted in-jokes, including one where the adult John gives his childhood playmate a stock tip across the years (Yahoo) which ultimately makes him rich. The story itself is burdened with an overload of MTV-type shots and edits, that just serve to clutter up the film, but the sequences of Frank in the fire are amazingly powerful and frightening, as is a confrontation between the serial killer and, not Frank, but John, at the police station. Don't ask.