“Upstream Color” is now playing at Sundance Cinemas. Not rated, 1:38, four stars out of four. I’ll be doing a post-show chat following the 7:05 p.m. show Monday at Sundance Cinemas.

At heart, “Upstream Color” is about a woman who escapes a controlling relationship and finds love with another equally damaged soul.

It’s just that the controlling relationship involved mind-controlling worms, the new love affair seems to be connected with psychic pigs, and “Upstream Color” is like no other movie you’ve ever seen. Even if you loved writer-director-star Shane Carruth’s mind-bending first feature “Primer” back in 2004, you might be utterly befuddled by his long-awaited follow-up.

While “Primer” was narratively dense, it was a time-travel thriller that traveled down a set of tangled but discrete narrative pathways, if you took the time to sort them all out. “Upstream Color,” meanwhile, is much more abstract and elliptical, leaving fuzzy patches in the story for the audience to make connections. Some might find that frustrating; I found it one of the most invigorating and intoxicating movie experiences of the year.

The first 20 minutes or so, I think I have a pretty clear handle on. Kris (Amy Seimetz) is abducted by a man (known only as The Thief in the credits) who forces her to ingest a small parasite that gives him absolute and total control over her mind. He can convince her not to feel hungry even if she hasn’t eaten for days, convince her to copy pages and pages of Henry David Thoreau’s “Walden” without question, and, oh, he can get her to turn her life savings over to him. It’s a scary sequence, seeing how completely Kris’ will and identity is turned over to a stranger, all because of a little mealworm.

When The Thief has drained her dry, he leaves, and Kris is left to pick up the pieces of her life. The worm in her body is drawn out by a pig farmer (Andrew Sensenig, known in the credits as The Sampler) who implants it in one of his animals. Here’s where it gets hazy — the worms seem to retain some kind of psychic residue of its human host, and The Sampler can use sound effects to access those memories. It’s seemingly a more benign form of mind invasion than The Thief’s, but no less intrusive.

Kris falls in love with Jeff (Carruth), who it turns out has been through the same experience with The Thief and The Sampler. What surprised me in the midst of all the sci-fi overtones is how raw and affecting their relationship is — Kris’ abduction has filled her with a rage-filled wariness at others, and the pair chafe and snap at each other before finally finding some kind of harmony. Amid all the narrative arabesques and visual splendor of “Upstream Color,” the honesty of that relationship, and especially of Seimetz’s performance, shouldn’t be overlooked.

“Upstream Color,” as far as I can tell, is about realizing that unseen, distant forces have a powerful hold on your life, and figuring out a way to wrest control back again. Or not — this is a film that leaves things way open to interpretation, and I would hate to impose my narrative upon the one you find. (That would certainly run counter to the theme of the film, wouldn’t it?)

While “Primer” was made for $7,000 and looked like it was built in a garage, “Upstream Color” is flat-out beautiful to look at, Carruth composing images with a Terrence Malick-like attention to depth of field and light. Images of the natural world — the worms, those cute pigs, and an unearthly blue orchid — play a major part in both the story of “Upstream Color” and its visual aesthetic. Watching it feels, in the best way, like a form of hypnosis.