YOU don't have to do this," someone tells Denzel Washington's agent. "Maybe I already have," he replies. He's preparing to go back to the past to prevent the bombing of a crowded New Orleans ferry using a sort of time machine that can replay the past from four-and-a-half days ago.

If this sounds complicated, it is. A huge suspension of disbelief is needed and director Tony Scott, eschewing most of his usual flashy visual gimmicks for a more straightforward approach, more or less gets away with all the scientific mumbojumbo behind this time-tripping. But to begin in the past - the opening scenes show the explosion and sinking of the ferry with huge loss of life.

Washington's ATF (Alcohol, Tobacco and Firearms) agent is seconded to a special team, headed by Kilmer, investigating the act of terrorism. Halfway through, this turns into a lecture on time windows and wormholes. Or something like that.

Washington plays the bemused onlooker to perfection, echoing the audience's own confused feelings at learning of the time travel theory. Fortunately, a big car chase is demanded to take our minds of quantum physics or whatever it is they're trying to explain.

But no ordinary chase as it takes place in the same place at two different times, four days apart. Washington displays dogged determination as agent Doug Carlin, who ends up going back in time to try to save the girl (Patton) we first see on the slab at the morgue.

Caviezel turns up late in the day as the bomber who's not easily stopped despite Carlin's timely intervention.

You might not believe or even understand Deja Vu but there's no denying that Scott has created an original action thriller that keeps the adrenalin pumping and the mind guessing until the end.

Stars: Denzel Washington, Val Kilmer, Paula Patton, Adam Goldberg, Jim Caviezel
Running time: 126 mins
Rating: Four stars