You have to pay close attention when watching Closed Circuit, a compelling, if sometimes convoluted, contemporary political thriller. If you scratch your head, you might miss something.

Closed Circuit revolves around a bombing attack in London and the subsequent high-profile case against one of the captured terrorists. Let’s just say, you will learn more about the British justice system than you may care to. The defense team representing the suspected terrorist, Farroukh Erdogan (Denis Moschitto), includes barrister Martin Rose (Eric Bana), who comes to the case six months in after the previous barrister mysteriously kills himself, and Special Advocate Claudia Simmons-Howe (Rebecca Hall). A Special Advocate is someone who is assigned to a defendant when that defendant is involved in some kind of national security breach. The SA’s main purpose is to review top-secret documents pertaining to the case, and these “closed materials,” once they are released, may only be discussed between said SA and the judge in a closed court. This means Claudia, once she’s handed the materials, cannot have any contact whatsoever with Martin until a verdict is reached.

This presents a dilemma because Martin and Claudia were once lovers, and in this situation, that’s naturally kind of a no-no. The two decide not to divulge their past history to the court’s higher ups, but honestly, that’s the least of their problems. The case stinks of political conspiracy from the get-go, and the more Martin and Claudia begin to peel back the layers, the more they see how far up the chain of command it goes.

The first two-thirds of the film gives us this inside view of the British legal system, and it is both fascinating and confusing. I felt a little like an American idiot, trying to figure out who does what and marveling at the fact they still wear wigs and robes in court. Unfortunately, Closed Circuit doesn’t know exactly what it wants to be. Once we get to the dangerous parts in the final sequences, the sense of urgency has been dampened. There have been other, better movies of this ilk that have had a broader appeal, such as the Clive Owen starrer The International, or the Nicole Kidman film The Interpreter; Circuit can’t quite measure up.

The film’s one major plus is in its performances. Bana and Hall do a superb job in their roles, particularly Hall (The Town; Vicky Cristina Barcelona), who conveys a steady, slightly flawed but extremely tough demeanor. Maybe if the film had simply stuck with the courtroom drama genre, it would have had a bigger impact because Hall just zings in those scenes. Bana also never lets you down. His Martin is intelligent, resourceful and thorough in his job. But Martin also knows when to give up if the situation becomes too dangerous, which isn’t what a usual hero does. As for the supporting roles, the young Hasancan Cifci is effective as the terrorist’s conflicted 14-year-old son, while British character actress Anne-Marie Duff turns in a surprisingly deceptive performance as someone who isn’t what she is initially thought to be. On the flip side, the usually-wonderful Jim Broadbent appears to be wasted as Britian’s Attorney General.

While the formality of the British justice processes may intrigue some, like me, Closed Circuit isn’t really for mainstream audiences. It’s a niche film for Anglophiles who enjoy a narrowly focused, if flawed, political thriller with smart dialogue.