This is not the review that will tell you to avoid a Jessica Chastain movie. Chastain's take-no-prisoners, full-throttle performances are a pleasure in themselves, and she is at a stage of her career where she can do no wrong. Somewhere in the next world, Joan Crawford and Bette Davis are actually agreeing on something, and it's that they really, really like Jessica Chastain.
So thinking of it this way, as a Chastain vehicle, "Molly's Game" is not bad at all. It allows her to be strong and forthright, to play surface amorality and inner moral fortitude, while doing as many flattering costume changes as she can cram in.
But "Molly's Game" aspires to be more than that. Thus, writer/director Aaron Sorkin takes a sordid, morally muddled anecdote and inflates it with an importance it doesn't deserve and can't sustain.
The movie tells the fact-based story of the real-life Molly Bloom, a young woman from a middle-class background, whose parents wanted her to become a lawyer, but she wanted adventure. She was an Olympic-level skier, but an injury ended her career.
When we first meet her, she is being arrested by a team of FBI agents who are pointing machine guns at her and showing her a piece of paper that says "the people of the United States versus Molly Bloom." When you get all the people of the United States mad at you at once, that's never a good thing.
In flashback, with a liberal use of voice-over, we get the story. Instead of going to law school, young Molly moves to Los Angeles. She becomes the assistant to a guy running a high-stakes poker game involving various (unnamed) celebrities, business and underworld figures. Because her boss is a nasty guy, and because she is smarter than he is, she takes over the game and moves it from a dark club to a luxury hotel suite.
We end up finding out more about poker games than we want to know, but some of the information is interesting. Apparently, it's not illegal — or sort of not illegal — to host a poker game. But if you skim a small percentage off the top, Uncle Sam takes offense. That's the source of Molly's legal troubles.
In between flashback scenes showing her expanding poker empire, we get many scenes of Molly conferring with her lawyer, played by Idris Elba; and this is where Sorkin reveals his weakness as a first-time director. He uses arguments for exposition and rapid-fire banter to explain arcane particulars of the poker world. Yet at least half the time, it's impossible to follow what they're talking about. Sorkin's default, when in doubt, is to steamroll the audience with dialogue. A more experienced director wouldn't do that.