On Sept. 18, 1961, U.N. Secretary-General Dag Hammarskjöld died when his plane crashed in Ndola, Rhodesia. The tragedy was officially deemed an accident, although almost immediately afterwards rumors began to spread that the actual cause of the calamity was foul play—say, perhaps, via a bomb, or a fighter jet that shot down Hammarskjöld’s craft. In Cold Case Hammarskjöld, director Mads Brügger goes in search of the truth of Hammarskjöld’s demise, and what he uncovers is a plot involving secret paramilitary cabals, covert-ops training facilities hidden in deep forests, Ace of Spades calling cards left by government executioners, and vaccines used to spread AIDS throughout South Africa’s black population.

In total, it makes for a fascinating spy movie-esque story—which doesn’t, however, mean it’s true.

Cold Case Hammarskjöld is a fascinating look into an age-old mystery that, in both form and content, doubles as an inquiry into itself—and, consequently, documentary filmmaking. Premiering in theaters on Aug. 16, Brügger’s non-fiction effort lays out its knotty modus operandi from the outset. First, it employs animation to depict the crash itself. Then, it presents the director decked out in the very sort of all-white ensemble that, he claims on camera, the villain of his story wore, in the same Congo hotel room he’s presently in—information that he narrates to a black female secretary sitting at a typewriter. As quickly becomes clear, Brügger is actually recounting his tale to two different black secretaries, in two different rooms, for unknown reasons. And as he admits, his subject matter is either “the world’s biggest murder mystery or the world’s most idiotic conspiracy theory. If the latter is the case, I am very sorry.”

Such is the dizzying confusion generated by Cold Case Hammarskjöld, whose initial concern is the aforementioned death of Hammarskjöld, whose desire to empower newly independent African nations, according to Brügger, ruffled the feathers of the UN’s old white colonialist corporatist guard. When his plane crashed, the secretary-general was headed to meet with Moïse Tshombe, the leader of Katanga, a region that was trying to break away from the Congo, and whose rebel forces had successfully defended themselves against prior U.N. military operations. Pilot error was blamed for the disaster that killed Hammarskjöld, and most of the world accepted that explanation. One individual who didn’t, though, was Göran Björkdahl, whose father was a diplomat working for the U.N. at the time, and had in his possession a metal plate that allegedly came from Hammarskjöld’s plane—and which featured numerous small holes that, Björkdahl surmised, might have been created by gunfire.

Thus began Björkdahl ‘s investigation, which Brügger embraces with a gung ho enthusiasm and curiosity that’s hard to resist—if, also, easy to view with a somewhat jaded eye, given the filmmaker’s prior ploy-heavy documentary The Red Chapel. What the duo discover are suggestions and accusations of a potentially explosive (no pun intended) sort. Most of those are related to the South African Institute for Maritime Research (SAIMR), a shadowy paramilitary organization first publicly mentioned by Desmond Tutu and other officials at South Africa’s final Truth and Reconciliation hearings in 1998. There, they discussed a 12-page SAIMR document which indicated that Hammarskjöld had been taken out because he’d become “troublesome.” British and U.S. intelligence agencies were apparently implicated by this manuscript, but the original copy of the bombshell report went missing.

Brügger and Björkdahl’s sleuthing isn’t deterred by a lack of concrete evidence, and the two are soon plunging down a rabbit hole filled with ever-wilder tall tales, most of which revolve around Keith Maxwell (i.e. the villain in the white suit), also known as “the Commodore,” who was the supposed founder and leader of SAIMR. Anecdotes abound about Maxwell posing as a doctor and establishing clinics throughout Africa, where he experimented on poor black citizens—including, possibly, giving them injections of AIDS in order to exterminate the black population and maintain white supremacy on the continent. Maxwell also trained SAIMR recruits to destabilize foreign governments and carry out coups at a clandestine compound where everyone dressed in white.

According to some, Maxwell was a ruthless mercenary. Yet the further Cold Case Hammarskjöld heads down this path, the more it seems as if he may also have been a “mentally ill” figure with fanciful notions about his own role in global affairs—an idea underscored by the highly-embellished biography he penned about his exploits, which Brügger dramatizes via animated sequences in order to highlight their suspect nature. The tension between what’s real and what’s fiction only mounts from there, to the point that the director admits he has no idea if anything he’s uncovered is authentic, and that his formal stunts—including chronological time-hopping, trying to excavate the wreckage of Hammarskjöld’s plane, and employing two secretaries for scenes where he narrates the outline of his movie—are merely ways to distract attention away from the emptiness of his entire endeavor.

Whether Cold Case Hammarskjöld is an exposé of nefarious malfeasance or a trip down crackpot lane is never quite clear, both to its benefit and detriment. Brügger lays out a reasonably persuasive hypothesis about the motivations behind an orchestrated hit on Hammarskjöld, whose corpse is seen decorated, in one photo, with a playing card that might have been a CIA-execution calling card. At the same time, there’s a lot of circumstantial smoke and not much actual fire to these accusations, and Brügger seems to compensate for a lack of proof by drowning viewers in names, and accounts, that expand the story—and plausibility—to the breaking point. Like his highly unconventional non-fiction approach, in which traditional archival footage, on-the-scene material, and talking-head interviews are thrown into a blender (and come replete with wannabe-funny asides that land with a thud), Brügger flip-flops between persuasive reality and outlandish make-believe, until the two are almost indecipherable from each other.

As a result, Cold Case Hammarskjöld is often most compelling as a self-referential study of non-fiction devices and motives, and the way that they can twist a story in numerous, sometimes deceptive directions (Brügger himself says he’s primarily drawn to Hammarskjöld’s death because of its espionage-ish elements). The truth is out there, Cold Case Hammarskjöld ultimately surmises—if not easily found.