At first glance, Deb (Sienna Miller) is all-too-easily dismissed. She’s a former teen mom turned grandmother at 31. She’s a mistress whose hot date turns out to be a trip to a sleazy motel room, where she is handed a plastic bag containing either dollar store lingerie or a slutty devil halloween costume (same difference, really). The next morning, we see that she is waking up alone in her own bed, suggesting the motel room was paid by the hour.

At that point, we’re about five minutes into American Woman, and you’re ready to write Deb off.

But don’t. Don’t you dare.

Because Deb is worth more than she even knows, which she stars to discover after her daughter fails to come home one night after a date with her basement-dwelling baby daddy.  A loved one’s disappearance must be life-shattering. Miller lets us see the dissapearance’s drastic effects on Deb in such a restrained and measured way that Deb’s resulting character growth is organic, believable, and most impressively, almost invisible at first. Deb’s evolution is captivating, and the Deb we know by the end of the movie is at once the same core character and a woman whose outlook and attitude have evolved beyond anything I could have ever expected.

I cannot overstate the magnificence of Sienna Miller’s performance in American Woman. She is magnetic and conveys a mix of strength and vulnerability that is as authentic a performance as I can remember. And while Miller is the standout, he excellence is almost always matched by the rest of the cast, including Christina Hendricks as Deb’s sister, Amy Madigan as Deb’s mom, and Mad TV’s Will Sasso as Deb’s brother-in-law. Deb is rightly the focal point but it’s great that the strong supporting characters each get the chance to shine.

The gauntlet thrown down by the cast’s fantastic performances is picked up by those behind the camera, and they are up to the task. Brad Ingelsby’s script is smarter than it has any right to be, discarding obvious answers on a regular basis, and showing off by giving effortless depth to secondary and tertiary characters (including turning an obvious villain into an earnest guy deserving of our sympathy). Director Jake Scott uses care and moderation rather than flash and sensationalism, particularly in a crucial scene at the film’s climax, proving beyond any doubt that less is more. Scott consistently makes brilliant choices even in small details, such as by using visuals and settings to indicate the passage of time, rather than title cards.

The result of all of this individual brilliance, naturally, is a standout character study that can hold its own against anything that TIFF18 has to offer (which I can say with certainty since I saw If Beale Street Could Talk and Roma on either side of it). American Woman is as smart, rewarding and satisfying a cinematic experience as anyone could ask for, making for a film that you absolutely do not want to miss.