Autumn, in “Never Rarely Sometimes Always,” is the most withholding movie protagonist since Anthony Hopkins in “The Remains of the Day.”

Like Hopkins’ character, a reserved butler, Autumn would be horrified to realize she’s at the center of a movie. Throughout “Never Rarely,” her goal is to keep her head down, escape notice, reveal nothing. A main character who doesn’t want to disclose any of her secrets could be a problem for a movie — where, presumably, we’re there to learn those secrets — but first-time actor Sidney Flanigan’s performance is so detailed and varied in its restraint that we can’t look away.

You may want to, though. “Never Rarely” is a challenging movie (once planned for theaters, it’s debuting on video-on-demand platforms). That’s because of its subject: Pennsylvania teenager Autumn, accompanied by her cousin, takes a hazardous journey to New York in order to get an abortion because her home state requires parental notification (she has reason to believe she can’t tell her parents).

Also, it’s challenging because of writer/director Eliza Hittman’s insistence that we can only understand how much is at stake in this woman’s trek if we experience every grueling, invasive minute of it with her. (Hittman’s last movie was the equally complex, equally unflinching study of teenage boys, “Beach Rats.”)

“Never Rarely” clearly is in favor of a woman’s right to choose but it’s not didactic. Workers at Autumn’s small-town clinic are not completely candid with her but they are kind; when Autumn gets to New York, the health care professionals she visits are helpful, albeit harried and startled by her lack of knowledge. Her biggest ally, cousin Skylar (Talia Ryder), with whom she shares an unspoken bond that resembles the one twins are said to have, is a rock.

In many ways, Autumn’s trip goes as well as it could for a teenager forced to flee to another state for health care. And, yet, the journey is still perilous. Because she’s so clearly vulnerable, we’re hyper-aware of the threats around her, from an opening scene in which she’s heckled by a vile classmate to a vaguely menacing man who confronts her and her cousin. It feels almost like the world is conspiring to make Autumn — and probably a lot of other teenagers — warier and more silent than she already is.

That’s why many secrets never do get revealed in “Never Rarely,” including who the father is (there are a couple of possibilities, both disturbing). It’s a tough movie to watch, especially since we know that lots of women have even fewer resources than Autumn. But “Never Rarely,” a prize winner at this year’s Sundance and Berlin film festivals, is not without hope. Every minute of the movie reminds us that Autumn has the strength and intelligence to stand up for herself.