Extinction event isn’t really a term you ever want to hear, particularly if you’re a human living somewhere on the outside of the Repopulation Center in Grant Sputore’s sci-fi family drama, I Am Mother. On the other hand, once the mysterious cataclysm thundering through the opening scene is over, inside the Center, at least one lucky embryo (of 63,000 in cold storage), soon to be known as Daughter, will be fortunate enough to be chosen by the digital stork and to grow up with all she needs in the loving arms of…a robot. Named Mother. Who is tenderly voiced by Rose Byrne.

In the early years, Daughter mostly doesn’t seem to mind being an only child, particularly with such a giving guardian. Sure, she wonders, as we do, why, with all those thousands of other options on hand, she can’t have even one brother or sister. But Mother soothes her, blaming herself for her own inexperience raising kids. When Mother’s proved (to who?) that she can be a good parent, they’ll be ready to hatch a few siblings. In glass wombs! In just 24 hours!

But then, before you know it, Daughter’s a teen, and she’s getting bored being in the house all the time, watching reruns of The Tonight Show. (Don’t we wonder what she’s learning about human behavior from this? Does she get irony? Does she imagine herself with Johnny’s white hair, think about aging, death? Wouldn’t she have a few questions about Johnny and Ed’s off-color banter that might break up those boring medical ethics lessons Mother insists on? I mean, it’s not like there are any other humans around to care about anyway, right? As if!)

But wait! Is that someone knocking on the air lock? OMG…it’s Hilary Swank! Gutshot and needing surgery, so all that medical training had a purpose after all!

But didn’t Mother say all the real humans were wiped out by a virus or something? And that they were bad because they screwed up the world? Could she have lied, like Hilary says? I mean, she seems cool. Or is Hilary Swank the liar? Can’t somebody just tell the truth for once? I’m so confused!

No. Wait. Sorry. It’s Daughter that’s confused. We, on the other hand, are simply hooked by this film’s fascinating turn on familial love and growing up. Of course Mother lies to protect her baby. That’s what parents do. But only until she’s old enough to handle the truth. To make the right decisions. What business does Hilary Swank have mucking things up, like she’s some kind of friend to Daughter or something, maybe even an alternate mother? So what if they’re the same species…that they’re a species! Mother is just trying to do her best, for the good of her daughter and the planet, which wouldn’t be in this shape if it weren’t for you lousy…. What more do you want?

I Am Mother really is a satisfying and thoughtful watch, with plenty of great camera work and effects, and fine performances from Swank and Clara Ruugard as Daughter. Mother’s anthropoid suit (it’s a dude inside!—Luke Hawker!) is a pretty genius piece of craftsmanship, too. It looks sort of like Honda’s ASIMO in wedge heels, but it’s three times his size and has the profile of a bodybuilder. Mother may be capable of a disarming, well-timed smile, but she’s threatening as…well…a mother when she gallops at a full tilt to protect her project…I mean…kid.

Despite being minimally humanoid in terms of a face, Mother’s body convincingly performs all the roles we project on our mothers: protector, teacher, nurse, threat. You really don’t want to disappoint her, but once your life and the human race is at stake, it’s still hard to break away. Then again, are you certain she has ill designs? There’s a constant sense of instability here as we struggle to understand what protection means in the world of this film, as we recall all the bent little half-truths we were told to keep us safe back then. And we turned out all right, didn’t we? You’ll have to go to theater to see if the same is true for Daughter and her passle of brothers and sisters. You’ll have the opportunity, no doubt, so don’t miss it.

See all our Sundance coverage here.