Uday Hussein represented the very worst of his father's despotic reign over Iraq, and that's saying something. The elder, less disciplined son of Saddam, Uday was a notorious sociopath the world is unquestionably better off without. He abducted and raped schoolgirls; he slaughtered his father's food taster and close ally at a party for the wife of Hosni Mubarak and did so in front of the guests; and he ordered the torture of Iraqi Olympians who failed to win. He may have even participated in that torture.
But before he became wildly unpopular, even within his own family (his father imprisoned him at one point), Uday adopted a body double named Latif Yahia. Saddam reportedly had several doubles, but we know of Uday's primarily because Latif Yahia eventually escaped Iraq and wrote a book about his experiences called The Devil's Double. Uday and Latif were classmates in high school, and years later, Uday pulled Latif out of the Iraqi army, made him an offer he couldn't refuse, and ordered some plastic surgery to complete the effect. It's a fascinating story, and for about an hour, it's a fascinating movie, thanks primarily to Dominic Cooper.
In a dual role, Cooper (Mamma Mia) does the remarkable. Perhaps because he's a lesser-known quantity than some actors doing the same thing (think Nic Cage in Adaptation), Cooper gives two distinct portrayals, and it never feels like it's a gimmick; these are just separate performances. The difference in them is clear just by looking at the actor at the beginning of a scene. In a better film, Cooper's work would receive a lot more attention than it will here, but director Lee Tamahori (Die Another Day) wanders off, through a brutal and intense story, to a sickly little ending.
Tamahori sidetracks The Devil's Double by relying on a very strange love triangle that involves Uday, Latif and a woman who may or may not be one of Uday's concubines. Sarrab (Ludivine Sagnier) appears to be just as kept as any other woman in Uday's gaze, although she is wildly flirty. Toward the end of the film, however, there's something of a piñata scene: One well-placed shot and way too much information comes flooding out. It's poorly timed and executed even worse: There is no precedent anywhere in the film for it, and it does not enhance the story of Latif Yahia in any way. It's a wild goose chase.
While the decision to go with a mostly unheralded British actor to play the dual role pays big dividends, Sagnier is completely out of her element here. She's a French actress speaking English with a thick Middle Eastern accent on top of it, and her dialog is almost impenetrable. She is also given so little to do for the first two-thirds of the film that it really underscores what a terrible decision it was to try developing this subplot into some kind of explosive conclusion. If the character is a requirement, then at the very least it has been poorly cast.
Sarrab's storyline is not the only thing wrong in a movie that admittedly gets more than a few things right. There's also too much time spent establishing Uday as the bad guy, which, given his history, is probably overkill. Latif's efforts to escape become secondary, as if the real heart of the film were not Cooper's empathetic half.