Suspense does not require loud sounds or frenzied bombast, and what isn't said is often more powerfully suggestive than what is. Writer-director Kelly Reichardt (2008's "Wendy and Lucy" and 2011's "Meek's Cutoff") understands this with every fiber of her filmmaking sensibilities. An auteur favoring naturalistic minimalism over silver-screen artifice, she stays true to herself with "Night Moves," but also exhibits a willingness to grow and explore beyond what her past projects offered. The observational deliberateness of her storytelling and the disciplined silences with which the narrative unfolds prove to be enormous assets, simmering with sustained tension. It is difficult to discern where things are going until they happen, and all that is missing is Bob Seger's same-titled 1976 pop chestnut. This is a masterfully concocted thriller.

Josh (Jesse Eisenberg) and Dena (Dakota Fanning) are Oregon-based environmental activists living among tight-knit local agricultural and health spa cooperatives. Busying their time with growing their own vegetables and supporting their friends on cautionary documentary projects, the two have recently branched off with a radical scheme to blow up the Green River Dam. It is a dangerous next step with a lot of uncertain variables, but one that they believe is necessary in a world where people, as Josh says in disgust, "kill salmon just because you have to run your iPod every fucking second of your life." Procuring a boat and fake IDs, they team up with a third accomplice, former U.S. Marine Harmon (Peter Sarsgaard), as preparations for their undercover act of eco-terrorism gets underway. What happens next will test their wills and their very humanity when all is done and they are left to question whether the reckless decisions they have made have been worth the sacrifice.

A potboiler of mounting paranoia as well as a study in the things people are capable of when they start living out of fear, "Night Moves" starts unsuspectingly and proceeds to raise the stakes. With the voices of their characters barely lifting above a whisper—no one, it should be mentioned, is conceived as a black-and-white hero or villain—Reichardt's and co-writer Jon Raymond's step-by-step account of what Josh, Dena and Harmon foolishly believe to be a victimless crime proves transfixing. When Dena faces off against a feed factory clerk (James Le Gros), trying every angle she can to coolly convince him to sell her 500lb. of ammonium nitrate fertilizer without a social security card, the results are so intense it is impossible to look away. The same could be said for a brush with an overly talkative hiker (Lew Temple), a run-in at a police checkpoint, and key confrontations and plot developments in the second half best left unrevealed.

Jesse Eisenberg (2014's "The Double") and Dakota Fanning (2010's "The Runaways") largely carry the film, backed by a seamlessly intriguing turn from Peter Sarsgaard (2013's "Blue Jasmine") as an acquaintance of Josh's committed to their cause. The supporting actors who fill out the peripheral roles are note-perfect in their authenticity, too, but it is Eisenberg's and Fanning's haunted portrayals of well-meaning yet misguided extremists Josh and Dena who electrify. Per Reichardt's artistic preferences, the performers are asked to avoid acting and instead simply exist in front of the camera as the people they are playing. It is a process that pays off here, the pair finding layers of vulnerability, determination and ruthlessness in their readings of gray-area protagonists who are neither lovers nor friends so much as business associates ill-equipped to handle the repercussions of their actions. Josh and Dena start the picture with the assuredness of young adults who think they know everything. They end it in places that sting with understandably unsettled mistrust.

"Night Moves" is Kelly Reichardt's most accessible feature, to date, and also arguably her most accomplished. In scenes such as one where the camera pulls up to loom sternly and suffocatingly over Josh as his troubled conscience weighs down on him, she and cinematographer Christopher Blauvelt (2013's "The Bling Ring") integrate their provocative thematic and stylistic intentions into a stickily complex whole. Without blatantly casting judgment on her characters, Reichardt allows her imagery to do the talking, subtly, pointedly and auspiciously arriving at a destination as pessimistically valid as it is staggeringly loaded. The remarkably suggestive, threateningly ambiguous last shot is the unforgettable finishing touch. Low-key does not mean slow and sluggish. The deliciously unnerving "Night Moves" confirm this with a potent right hook.