Documentary from the actress-director, in which she explores her own family history.
It had long been a running joke at the Polley dinner table that Sarah looked less their father than any of her siblings, and when Sarah finally hears of the rumors that her actress mother (now deceased) may have had an affair with a co-star while out of town with a play, she decides to investigate.
And that's really all you should know about the story going in. There are surprises, unexpected revelations, delightful punchlines, complicated characters, and beautiful moments of painful honesty as the truth unfolds. It's a marvelous story, and Polley tells it in creative and entertaining style.
It will be interesting to see whether the Motion Picture Academy's Documentary branch chooses to nominate this for an Oscar; there are some storytelling choices that might have purists questioning whether this is really a documentary at all. I think that would be excessive quibbling; the movie certainly deserves a nomination.