Right now it is tempting to find parables and parallels everywhere for the current US situation. With this documentary from Nanette Burstein, the zeitgeist-paranoia is justified. Her film is about a man who, in political terms, was John the Baptist to the non-Jesus that is the president-elect.

One of the candidates running for the US presidency in the early stages this year was a very rich, entitled and arrogant businessman with a huge social media presence, what this film suggests is a troubling attitude to women, a strong “eccentricity” (rather than the simple madness of lesser, poorer people) and a tendency to get riled by the media.

This was John McAfee, the 1980s antivirus software tycoon who had retired in the noughties to run a yoga retreat on his vast Colorado estate. After apparently losing a bundle in the crash of 2008, he emigrated to Belize where he jokingly told reporters he was going to be like Kurtz in Conrad’s Heart of Darkness. According to this documentary, he proceeded to pay off the cops, put dozens of local gangsters on the payroll as armed bodyguards, nurse crazy schemes to develop new-age medicines from indigenous plant life and cultivated psychopathic levels of paranoia about being kidnapped – he appeared to become a would-be king of the Central American jungle.

He then became wanted in connection with the murder of neighbouring US national, as well as, according to the claims made by one of Burstein’s interviewees, having a horrendous case to answer concerning sexual assault, and the now notorious “gringo” McAfee went on the run in Guatemala. He finally made it back to the US, where he found the Belize government did not have the evidence to pursue extradition, and without a scrap of humility, penitence or self-awareness he relaunched himself as a hip, Ted-talking online privacy guru with a spurious rebel cachet and a monster Twitter following. Then he got it into his head to run as an independent candidate for the White House. (Authorities in Belize fiercely deny any suggestions of impropriety and maintain McAfee is not a suspect in the murder.)

One of the most grimly funny parts of Burstein’s film is squad-car footage of McAfee being pulled over in 2015 for drunk-driving and telling the cops his name and assuring them they must surely have heard of him. His fame appears hugely important to him: it feeds what seems to be a deeply creepy, scary fanaticism.

Burstein tells the story of her contact with McAfee through her Facebook messaging with him. His emails suggest a queasy mix of neediness, prickly aggression and serpentine malevolence. With patient interviewing, and in the face of some deeply nasty threats – McAfee actually sent her some covert surveillance photos he’d taken of her and her camera crew – Burstein uncovers some very important circumstantial evidence concerning his behaviour. But actually bringing him to court seems an impossibility.

Getting nowhere near the presidency was by no means a foregone conclusion for this nasty bully. His story is a very enlightening and important one; Burstein tells it well. McAfee had a proto-Trump quality of arrogance, yet was not quite rich enough or cunning enough, or indeed famous enough, to make it big. Maybe he could still be picked as a White House special adviser on cybersecurity.