Searching for Sugar Man (12A)

Sixto Rodriguez, in case you haven't heard of him, was a Detroit singer-songwriter, an "inner city poet," for whom great things were predicted in the early 1970s. Producers reckoned he was the equal of Bob Dylan. His first album, Cold Fact (1970), was supposed to be his breakthrough but failed to sell. His second, Coming from Reality (1971), didn't do any better. His record label dropped him. That's when his story became very strange indeed.

Swedish director Malik Bendjelloul's uplifting and very surprising documentary is so far-fetched that you half suspect he must be making it up. In the first half, he deliberately plays up the air of mystery. We hear all the urban myths about what may have happened to Rodriguez. The prevailing view was that he committed one of "the most grotesque suicides" in rock history, setting himself on fire or shooting himself at the end of his final gig. In America, he was a failure. No one paid much attention to whether he was alive or dead.

Among white liberals in late-apartheid-era South Africa, the case was very different. Somehow, his music reached the country and very quickly assumed cult status. The records sold hundreds of thousands of copies. The South African fans didn't know anything at all about him. Most assumed he had gone the way of Jimi Hendrix and Janis Joplin. They also assumed that he was as popular elsewhere as he was in Cape Town and Johannesburg. In a closed, repressive society in a pre-internet era, the fans had no way to find out more about him. His air of mystery added to his appeal.

British producers Simon Chinn and John Battsek, who are behind Searching for Sugar Man, have plenty of experience in making feature documentaries aimed at cinema audiences. (Their respective credits include such films as Man on Wire and One Day in September.) Here, what easily could have seemed just another talking heads rock doc about a marginal figure is given great dramatic impact by its stealthy structuring.

The film-makers deliberately conceal key information about Rodriguez until relatively late in the film. They also make the documentary into a detective story. We hear how South African investigative journalist Craig Bartholomew and record-shop owner Stephen "Sugar" Segerman painstakingly put the pieces of the Rodriguez story together. First, they tracked down his daughter and then they made the startling discovery that he was alive and well – and working in construction back home in Detroit. He had no idea at all that he was considered a superstar in South Africa.

It helps that Rodriguez's music stands up remarkably well. He is a Woody Guthrie-like balladeer writing songs that are angry, tender and humorous by turns. It's also to the film-makers' benefit that, for all his ostensible stage fright, he is remarkably charismatic when he is finally prised out into the open. With his long black hair, the Mexican-American singer-songwriter looks a little like Jim Morrison. He also still dresses like a rock star, even if he has been living a resolutely blue-collar life for the past 30 years, helping demolish derelict houses and lugging refrigerators up and down staircases. He is also politically active, with a Tom Joad-like zeal for standing up for the working poor.

We learn that his attempt at running for public office was even more disastrous than his music career in the US. He won only 139 votes – which, one guesses, must be on a par with the number of albums he sold. However, he shows no bitterness or regret. When he is lured to South Africa in 1998, he takes the adoration of the 20,000-strong crowd at his first concert in his stride. At the same time, he shuns the trappings of luxury that come with being a rock star – the limos and hotel suites.

Rodriguez is nothing if not inscrutable. The great South African journalist Rian Malan (author of My Traitor's Heart) was one of the first to interview him and tells the film-makers that he got "nothing." Director Bendjelloul doesn't fare much better in his on-camera encounters. Although scrupulously polite, Rodriguez either stonewalls or throws back the director's questions at him. However, his reticence isn't a problem. He has some of the same qualities as Peter Sellers' Chance the Gardener in Hal Ashby's Being There. He reveals so little that others are able to project their opinions and fantasies on him.

Searching for Sugar Man is a rare feature doc in which next to no one behaves badly. The record boss Clarence Avant, who is blithely dismissive about all the royalties Rodriguez has lost over the years, introduces the only note of cynicism. This is a story that sounds too good to be true – and yet, unless Bendjelloul is grossly misleading us – everything shown here really did happen. There are parts of the story that Bendjelloul leaves out, presumably because they might have lessened the dramatic impact. For example, Rodriguez wasn't ever quite as obscure as the documentary suggests. He had a following in Australia and toured there long before he went to South Africa.

The film poses nagging questions about the nature of fame and success. The reasons why Rodriguez flopped so completely in his American musical career are never explained satisfactorily. Some attribute his lack of popularity to his Mexican background. Others blame bad marketing or his undemonstrative stage persona. (He sometimes played with his back to the audience.) You don't understand, either, why his record producers, who all testify to his huge talent, didn't stick with him. However, Searching for Sugar Man is such a rousing documentary that it seems churlish to quibble over the details. Instead, like the awestruck South Africans who welcome Rodriguez back as if it is a second coming, we should take his astonishing story at face value.