We prefer our rebel heroes to start noble and stay that way. So when one plummets as spectacularly as did WikiLeaks founder Julian Assange, we want to know why. In the long but concise “We Steal Secrets: The Story of WikiLeaks,” Oscar-winning documentarian Alex Gibney avoids pat judgments while expertly laying out a real-life espionage thriller spotlighting the men behind the largest security breach in U.S. military history.

Gibney’s intertwined protagonists are Assange, an obscure Aussie hacker who achieved international pop-star status by, in his words, “crushing bastards,” and Bradley Manning, the troubled young Army private who passed along the war-related documents that shot WikiLeaks to fame in 2010. Manning’s leaks to Assange, including horrific video of U.S. soldiers matter-of-factly gunning down innocent civilians and journalists, became the subject of splashy accounts in the New York Times and major European media.

Although Gibney never spoke directly to Assange or Manning, he builds surprisingly intimate portraits of each, in Assange’s case through interviews with former colleagues and journalists.

Assange comes off at times like a tragic figure, a bottle-blond MacBeth corrupted by success, at others a creepy egomaniac in freedom-fighters’ clothing. Amid calls for his arrest on one side of the debate and hero worship on the other, Assange was accused of sexual assault by two women in Sweden. Though ample time is spent on this he-said/they-said controversy, more questions are raised than resolved.

The movie’s release is aptly timed, as Manning’s court-martial began this week. Assange remains holed up at the Ecuadorean embassy in London, seeking to avoid extradition to Sweden.

Skipping between Assange’s rise to power and Manning’s document-dump deception, Gibney builds a remarkable level of suspense, given how exhaustively WikiLeaks has been covered in the media.

He also raises telling questions on the handing of the case by both the media and the military. Why was Assange singled out as having “blood on his hands,” ostensibly putting military and civilian lives at risk, when the New York Times is equally and arguably more culpable? Why weren’t Manning’s superiors held accountable for allowing a demonstrably unstable soldier continuous access to highly sensitive military intelligence?

As an outsider Gibney does not, and probably cannot, provide the answers. But he takes a complicated saga and boils away unnecessary details, leaving as clear a picture as possible. He also underscores the problem with Assange’s noble — initially, at least — cause. No matter how well-meaning exposing truth for the greater good may be, revealing the whole truth — and nothing but — can be tricky business.