Brody is Jack Stark, a Gulf War veteran who takes a bullet in the head at the beginning of the movie. His narrating voice tells us that this marked the first time he died, which doesn't make much sense, because he doesn't die; he survives. He gets back to decent physical shape but winds up with amnesia, the first sign that screenwriter Massy Tadjedin's script might be a little trite.
A mishap involving a grown-up Brad Renfro (Brad is back!) gets Stark a stay at an insane asylum where the crazy Doctor Becker (Kris "The Growler" Kristofferson) has a very strange concept of what's good for his patients. He shoots them full of mystery drugs, straps them into straightjackets and leaves them to scream in a morgue drawer. This is to create a "womb-like" environment, a conflicted idea considering most of us could move around, had a food source and even listened to tunes via a speaker on the mommy tummy while in the womb.
While in the drawer, Jack travels ahead in time, where he meets Jackie (Knightley) who has a mystery identity that I won't give away here. Jack takes numerous trips into the morgue drawer; thus, he takes numerous trips into the future, where romance blossoms with Jackie.
Is the romance with Jackie just a figment of his overactive imagination, a side effect of drugs and isolation? Is he really taking a physical trip into the future? The screenplay throws in a bunch of coincidences that suggest Jack really is traveling, but it leaves things nice and ambiguous, perhaps hoping that a cult following will sit in coffee shops and come up with their own conclusions a lá Donnie Darko.
My guess is that director John Maybury's work here, while promising in spots, is not meaningful enough to have viewers take much away from the theaters. I've mentioned other time-travel movies, but the film The Jacket seems to rip the most from is Jacob's Ladder, that extremely creepy Tim Robbins film in which a soldier basically played a movie in his head as he laid dead on the battlefield.
Brody does a decent job looking disturbed and uncomfortable, something he showed a knack for with his Oscar-winning role in The Pianist. He hasn't gotten good roles since then--a small part in The Singing Detective, and his embarrassing turn in The Village. Peter Jackson has cast him in his upcoming remake of King Kong, so perhaps Brody will get a chance to breathe a bit and have some fun with that blockbuster.
Knightley is a bit overwrought at times, but that seems to be more a byproduct of the script and direction rather than her talents. She fashions a rather impressive American accent, and does a decent job looking and sounding drunk.
The movie, despite its complete lack of originality, actually works OK for much of its running time. By trying to tie up the film with a neat little bow in the final act, complete with a happy ending, Maybury and team basically chicken out. This ain't no Donnie Darko.