When the late malevolent rightwing carny Andrew Breitbart provides your sole positive character reference out of nearly a dozen people speaking about you—some of whom were once your best friends—you might want to re-think your existence. In director Jamie Meltzer’s mesmerizing documentary Informant, Brandon Darby—a onetime lefty activist darling turned FBI informant and rightwing spokesman—is slowly filleted by former associates. None, however, are more damning than his own documented actions, or the original interviews he gives Meltzer; he’s tense, combative, defensive, and unconvincing as he argues on his own behalf. As is true with many fallen heroes, Darby’s strength and Achilles heel were (are) one and the same. A handsome, magnetic alpha male, he’s also an egomaniac. As one former associate notes, that was the very quality that made him such an effective advocate for victims of Hurricane Katrina abandoned by the government. His work with the activist collective Common Ground on behalf of those Lower Ninth Ward residents thrust him in the media spotlight and made him a poster boy in certain far left activist circles. It also set in motion his professional (and arguably psychological) ruin. Filled with staged reenactments of crucial events in Darby’s trajectory from left to right (with Darby playing himself), lots of interviews with former friends and associates, and phone interviews with one of the men imprisoned on Darby’s testimony, Informant is riveting as it slowly assembles a damning profile of its subject. It’s also timely. As government spying and erosion of civil liberties both escalate, Informant serves as a cautionary tale for the amount of trust granted those who wield power in activist circles.