If you’ve seen a science fiction movie in your time here on planet Earth, you can probably guess where I Am Mother, Netflix’s new sci-fi thriller, is going.

Directed by Grant Sputore, the film begins in a repopulation center following an extinction event. A robot, referred to as Mother (physically performed by Luke Hawker and voiced by Rose Byrne), begins the repopulation process, raising a girl she simply calls Daughter (Clara Rugaard). Blindly trusting of her guardian, Daughter never questions Mother’s claim that the outside world remains too toxic, hence their confinement to the underground facility. That unconditional belief, however, wavers when a severely wounded stranger (Hilary Swank) arrives at the bunker doors.

[Ed. note: this review contains mild spoilers for the movie]

I Am Mother works off a blueprint that so many films featuring robots or single-setting dramas have before. It’s the “robots with feelings” aspect of I, Robot crossed with the contained nature of 10 Cloverfield Lane — it just falls short of either.

So long as the scope of the film (from a screenplay written by Michael Lloyd Green) remains small, I Am Mother maintains a tension that should keep even the most skeptical viewer hooked on the proceedings. Instead of conveying Daughter’s burgeoning doubt and the stranger’s hostility through jump scares and blunt action sequences, a slow, restrained implosion makes the proceedings unsettling. On top of that, Mother’s specific motivations may be called into question, but it remains difficult throughout the entire film to question her devotion to Daughter.

As I Am Mother expands into twist-laden territory, everything immediately begins to feel looser and more unwieldy. While the film keeps finding ways to make its relatively familiar story arc feel fresh, there’s so much action that occurs in its second half that, by necessity, it rushes through them. The little details — Daughter’s fascination with Johnny Carson, the childish stickers that were placed on Mother by the adolescent Daughter — are the most striking parts of the film, and the movie loses momentum as it leaves them behind.

Though there’s little point in bemoaning it now, I Am Mother feels like the kind of story that would have been better served as a TV series. To a certain extent, the film benefits from Sputore’s even hand, as nothing is ever over-explained and a few plot points remain relatively mysterious. By contrast, the twists that lead up to the ending (and seem to set up the possibility of a sequel, or at least some more granular explanation of Mother’s governing mission) are too broad to get away with that relatively hands-off approach.

Sputore’s direction is strong whenever he’s trapped in suffocating spaces. In a sequence that sees Daughter running through the bunker, Sputore takes advantage of how similar all of the facility’s passageways look to create a sense of continuing motion even as the shots cut between following Daughter and preceding her as she dashes down the hall. Daughter knows this bunker like the back of her hand, camerawork creates a sense of disorientation as her previous trust in Mother comes into question.

The film’s special effects are also best when contained. Mother, given form by a practical robot suit built by Weta, is always completely believable (Mother’s interactions with Daughter are seamless), but the more Daughter’s horizons expand, the worse her surroundings start to look, metaphorically and literally.

All three performances keep the movie from short-circuiting. Where Byrne is tasked with serenity, able to detect changes in Daughter’s pulse and her according spikes in nerves and anxiety, Swank’s performance lies at the opposite extreme. She’s unpredictable and messy where the facility and Mother are sterile. Rugaard is caught between them, raised to be perfect by Mother but human nevertheless.

I Am Mother doesn’t stick the landing, but it’s still impressive. The themes — humanity causing its own end, co-existence between artificial intelligence and living, breathing people, post-apocalyptic bunker drama — are old, yet the execution feels fresh by focusing on its characters and how their individual tics shape their experience of familiar situations. Like the robot at its center, I Am Mother is a lean, mean, machine.