Night Moves Jesse Eisenberg, Dakota Fanning, Peter Sarsgaard. Directed by Kelly Reichardt. Rated R. Opens Friday.

Kelly Reichardt has quietly become one of America’s greatest independent filmmakers, equally adept at probing character studies (Old Joy) and revisionist historical epics (Meek’s Cutoff). Unfortunately, her latest film, Night Moves, doesn’t play to her strengths.

Its first half is typically strong, introducing a trio of environmentalist radicals—Josh (Jesse Eisenberg), Dena (Dakota Fanning) and Harmon (Peter Sarsgaard)—who are plotting to blow up a hydroelectric dam as a protest against America’s wasteful consumption. A superb scene in which Dena attempts to purchase 500 pounds of ammonium-nitrate fertilizer from a suspicious cashier (James LeGros), played for maximum slow-burn tension, briefly suggests that Reichardt may be as skilled with genre as she’s proven with just about everything else.

At about its midpoint, however, Night Moves abruptly shifts gears to the aftermath of the dam incident (which doesn’t go exactly as planned), at which point the film slowly and somewhat ironically starts to run out of gas. Loyalties among the three protagonists are tested, but these people are unusually sketchy by Reichardt’s standards; it’s not even clear how long Josh and Dena have known each other, or whether they were once a couple. Shocking events seem imposed by the screenplay rather than driven by character. It’s a disappointment, but every great filmmaker is allowed the occasional noble whiff.