EVER feel like travelling back in time to wipe the slate clean? Denzel Washington gets the chance in Deja Vu, a sci-fi thriller in which he plays a federal agent who seeks to undo the bombing of a New Orleans ferry and bring back a beautiful woman found dead near the wreckage.

Cinematic time travel is nothing new, of course. There have been several movie versions of H.G. Wells's The Time Machine, not to mention three Back to the Future installments and last year's mangling of Ray Bradbury's A Sound of Thunder.Unlike those films, however, Deja Vu tries to explain some of the bewildering theories that might make time travel possible. My eyes glazed over at the first mention of quantum physics, though the more scientifically inclined may actually figure out what the geeks are talking about.

You don't have to be a rocket scientist to understand the basic story: Man meets dead woman, gets to know her through flashbacks, falls in love with her and sets out to save her by changing the past.

It's a tricky business, but who better to pull it off than the resourceful Washington, who in previous movies has helped capture a serial killer and track down terrorists. No one this side of Dick Cheney is better at living in the past than Washington's Doug Carlin, a loner called in to investigate a deadly explosion on a ferry filled with sailors and kids.

The probe leads Carlin to a bunch of brainiacs who appear to have hidden cameras that can look backward as far as four days. Using this too-complicated-to-explain technology, they can trace the dead woman's movements in the period leading up to the blast. This being Hollywood, we get to watch Claire (Paula Patton) take a shower and prance around her house in her underwear. While this may or may not yield crucial clues, it definitely beats listening to lectures on quantum physics.

The chief suspect turns out to be a Tim McVeigh clone, played with appropriate spookiness by Jim Caviezel. A military reject, the bomber has a grudge against the US government and believes that "sometimes a little human collateral is the cost of freedom".

Carlin climbs into a capsule and zips back in time to see if he can stop the madman from killing all those innocent folks, including his formerly dead, future girlfriend. As events unfold, we find out why Carlin kept having that "I've seen this thing before" feeling before hopping into the time machine.

Tony Scott, who also directed Washington in Crimson Tide and Man on Fire, keeps the action moving at a frenetic pace but squanders the New Orleans setting. (Deja Vu claims to be the first film shot in the Crescent City following Hurricane Katrina.) Other than a few skyline and riverfront shots, there's scant New Orleans atmosphere; it might as well be Cleveland or Seattle.

Val Kilmer is wasted in a supporting role as an FBI agent, Patton looks lovely dead or alive and Washington, as usual, oozes intelligence, guts and charm. If only those qualities were evident in the rest of the film.