When a movie is titled "Traitor," you know to expect a few twists.

Don Cheadle stars as Samir Horn, a man whose loyalties seem to lie mostly with himself. Born in Sudan, he watched as his father was killed in a car bomb. When we next see him, he is in Yemen, selling explosives to jihadists. He's arrested there and thrown into a hole of a jail, along with his would-be business associates.

Soon Samir is visited by a pair of FBI agents, Roy Clayton (Guy Pearce) and Max Archer (Neal McDonough). Samir has an American passport; if he'll tell the agents where he got the explosives, they can get him out. If not, he'll be left to rot.

No dice. Samir says he simply sells to the highest bidder, no matter who it is. After a punch in the gut from the hot-headed Archer, he's left behind.

Is Samir a traitor? What is the truth here?

As Samir says later in the film, the truth is complicated.

"Traitor," directed by Jeffrey Nachmanoff, is both a first-rate spy thriller and a commentary on what leads one to become a terrorist. The former element is more successful. While parts of the world may indeed consider the United States the true aggressor in the war on terror, if not a terrorist nation itself, the portrayal of that here is stock, cliched.

At least our weapons don't kill innocent people, Archer tells Samir.

Yeah, right, genius, Samir sneers.

And that's the lesson, presumably.

In prison, Samir is recognized as a truly devout Muslim by Omar (Said Taghmaoui), who befriends him and takes Samir with him in an explosive escape. Soon Samir is planning bombings, one of which he carries out himself, at the American consulate in Nice.

Meanwhile, Clayton and Archer are trying to piece together Samir's past. Turns out he was in the U.S. Army, with Special Forces. He returned to his Muslim roots while serving in Afghanistan. He has since gotten friendly with plenty of bad guys. Clayton, Archer and their bosses want him, badly, but Samir is hard to pin down in almost every way.

The story, by Steve Martin — yes, the wild-and-crazy Steve Martin — is gripping, and interestingly plotted. We learn more about Samir from Clayton and Archer than we do from the man himself. We also learn something about Clayton, a would-be third-generation Baptist preacher who instead opted for a Ph.D. in Arabic studies before landing in the FBI. Still, Clayton is somewhat underdrawn, giving Pearce less to do than he might have had.

Taghmaoui is quite good — his developing relationship with Samir is the heart of the film. Omar is a thoughtful man of fervent belief, yet he is willing to admit questioning himself on occasion. Jeff Daniels is also good in a small but crucial role as a CIA contractor.

But Cheadle is outstanding. That's no surprise; he's a fantastic actor. Here, he's given a lot of room in which to navigate. His portrayal of Samir, an immensely conflicted man, quietly establishes the character as a man of unwavering faith and loyalty. But loyal to what? And to whom? Those are the central questions. And the answers, as Samir says of the truth, are never easy.