Every couple of years or so, this reviewer is approached by a friend or acquaintance who is excited about some great new product that they’ve just quit their job to sell. Curiously, instead of trying to make me a customer, they’re always more interested in offering me an opportunity to share in their good fortune by becoming a distributor.

That’s a red flag that the business isn’t legitimate, but a pyramid scheme. Such an operation is easy to identify, because its participants profit primarily by recruitment rather than by the sale of goods or services to consumers.

Directed by Ted Braun (Darfur Now), Betting on Zero chronicles hedge fund manager Bill Ackman’s campaign to expose the health food corporation Herbalife as being a multi-level marketing Ponzi scheme. What makes the movie intriguing is that Ackman may not have been acting altruistically, since he had also shorted Herbalife by placing a billion-dollar bet that the company’s stock price would plummet.

Nevertheless, Ackman was considered a Robin Hood in working-class circles, because he promised to distribute any profits he might make — when the stock’s value plummeted — to the unsophisticated minorities who had lost their life savings that they had invested in the company. The millions of victims were predominantly undocumented immigrants who were afraid to report how they’d been fleeced to the authorities because they were afraid of being deported.

To prove his case, Ackman first needed to convince the Federal Trade Commission that Herbalife was indeed a criminal enterprise. That would not be easy, considering all the prominent individuals who were lobbying on behalf of the firm, such as CNBC investment adviser Jim Kramer, Donald Trump’s crony Carl Icahn, former Secretary of State Madeleine Albright, and ex-Mayor of Los Angeles Antonio Villaraigosa.

For instance, billionaire Carl Icahn not only propped up Herbalife’s stock by taking a huge stake in the company but even went on television to refute Ackman’s pledge to give his financial gains from short selling the stock to charity. Ultimately, the controversial case is resolved in one side’s favor, though it would be unfair for me to spoil the ending.

Is Herbalife a con game being run by shady snake oil salesmen, or a benign operation affording average people a realistic shot at the elusive American Dream? You be the judge.

Excellent (****). Unrated. In English and Spanish with subtitles. Running time: 104 minutes. Distributor: Zipper Bros. Films.