Michael Keaton has this incredible, I'm-at-the-edge-of-the-abyss look that should be taught as "the hangdog" in drama school.

The actor, who picked up an Oscar nomination for 2014's Birdman, flashes the look several times in the opening minutes of The Founder, director John Lee Hancock's fact-based morality play about fast food, fast money, and the ethics of corporate America.

Keaton plays McDonald's visionary Ray Kroc, whom we meet when he's an exhausted and exasperated middle-aged also-ran whose various get-rich-quick schemes have all amounted to a big, fat, fizzling nothing. He's grinding out something like a living driving from one Midwestern town to the next as a restaurant-equipment salesman.

Then one day, he sees the future of America's food industry, and he grabs it with both hands, with the desperation of a drowning man, and he holds on to it for dear life until it makes him a billionaire.

Kroc sees a small burger stand in San Bernardino, Calif., called McDonald's, where a cadre of disciplined young workers cooks and serves, within a matter of seconds, the best hamburger he has ever tasted. He meets its founders, oddball brothers Maurice "Mac" McDonald (John Carroll Lynch) and Richard "Dick" McDonald (Nick Offerman), who are able to offer such fast service because they assemble food the way cars are made on the assembly line.

It's 1954, and this meeting will forever change the face of the food industry in America.

Written by Robert D. Siegel (The Wrestler) and directed by Hancock with remarkable assurance and style, The Founder starts as a straight-up Horatio Alger story, the tale of a perennial underdog whose work ethic and tenacity finally make him a winner in the world of business.

The music is cheerful – all acoustic guitar twangs and solo piano notes – and Kroc's discovery of the McDonald brothers is handled with oodles of positivity and wit.

It's happy vibes all around.

But just when the film's relentlessly upbeat mood starts to bug you, The Founder starts to shift gears. The soundscape and color palette become darker, as does the story of Ray Kroc and the brothers McDonald.

If the first half recounted the travails of a lovable has-been who discovers a new lease on life, the latter part of The Founder shows what can happen when the underdog finally wins – only to become a tyrannical, narcissistic overlord.

And, boy, does Keaton's Kroc ever become mean, selfish, small-minded – though he's never less than fascinating.

Lynch and Offerman play off him beautifully as a pair of artisan small-business owners who are apprehensive when Kroc tells them he can make them a fortune if they allow him to franchise their restaurant.

Offerman is especially wonderful as Dick, an obsessive, monomaniacal perfectionist forever fiddling with a stopwatch looking for ways to maximize the efficiency of his burger-assembly line. The Founder also features a strong turn by Laura Dern as Kroc's first wife, Ethel.

It's in the movie's domestic scenes that it first betrays its dark edges: Kroc is clearly happier at work than at home and seems to have nothing to say to his wife. Enter Linda Cardellini in an intelligent, va-va-voom turn as Joan Smith, a businesswoman and future Mrs. Kroc.

If he had little patience for Ethel, Ray Kroc has even less time for the McDonald brothers, who fret and worry that he is compromising food quality in the name of profit.

The two sides eventually go to war over milkshake ingredients.

Eventually, Kroc writes the brothers out of the business – and out of history –  when he begins claiming that he alone founded the chain.

The saddest aspect of The Founder is our realization, during the instant we meet Mac and Dick, that the McDonald brothers already are dinosaurs, relics of an old American model of business where craftsmanship and quality were greater points of pride than profit margins.

Or perhaps that world never existed.