Josh and Dena are members of an environmental organization that holds the belief that restoring the environment cannot be achieved through singular monumental actions but rather through a series of smaller battles. Their current focus? They are convinced that a local dam is wreaking havoc on the surroundings and see this as their chance to contribute to nature’s restoration.
Radical environmentalists, Josh (Jesse Eisenberg) and Dena (Dakota Fanning), set off on a mission—after purchasing a boat, they embark on a journey to meet Harman, an ex-Marine played by Peter Sarsgaard. During their trip, they find a doe dead on the roadside, and upon inspection, discover the doe is pregnant, with a fawn still alive inside her.
With resolve, the trio plots to bomb the dam that they believe is detrimental to the ecosystem. They gather fertilizer, with Harmon already possessing 1,000 pounds, but he worries he is short by 500 pounds. Harmon is determined to buy more Ammonium-Nitrate fertilizer from a local feed store, although Josh is wary, as purchasing over 10 pounds usually raises red flags at retailers.
Despite Harmon’s hesitations about Dena's involvement, since she invested $10,000 in the boat under the agreement that she would participate in the operation, Dena’s commitment to the cause comes into question when she learns about Harmon’s criminal past over breakfast. This revelation causes a rift in trust, leading her to question Harmon’s intentions.
To acquire the fertilizer, Dena concocts an elaborate backstory about needing it for her imaginary 10-acre broccoli farm. At the feed store, she faces resistance when the clerk, played by James LeGros, demands her social security card. Harmon encourages her to persist, arguing that no legal requirement exists for such identification when purchasing fertilizer. Finally, Dena returns to the store and successfully convinces the clerk, claiming her crops are overdue and that multiple trips are unfeasible.
After assembling the bomb and cleaning up any evidence from Josh's pickup truck, they use it to tow the boat to the dam. They load a rowboat onto Harmon's truck to ensure their escape after deploying the bomb. Arriving at a secluded location, they witness the ecological destruction caused by the dam.
In the cover of night, they maneuver the boat close to the dam, arming the bomb before retreating in the rowboat. They encounter a minor setback when a couple struggles with a flat tire right by the dam, giving them a tense moment as they try to remain unnoticed. Fortunately, the couple manages to fix their tire and leaves without spotting them.
After the explosion, Harmon bids farewell and departs, while Josh and Dena narrowly escape police attention despite Josh's wet boots. Back at the farm, Josh learns from fellow residents that a camper near the dam is missing post-explosion. The locals speculate that even if the dam was destroyed, the impact on the local economy would be negligible since many other dams line the river.
Harmon later contacts Josh, expressing concern for Dena, who is evidently distressed. Dena confesses her guilt, hinting she might disclose their involvement to the authorities. Realizing the danger this poses, Harmon insists to Josh that Dena must be silenced. Meanwhile, the other farm inhabitants grow suspicious of Josh's role in the bombing, leading them to urge him to leave.
After Dena confides in someone from the farm about the events, Josh finds out that the missing man has been discovered dead, a victim of the flood triggered by their actions. Fearing Dena will go to the police, Josh tracks her down to her workplace, attempting to dissuade her from speaking out. However, a confrontation ensues, resulting in a tragic escalation where he ultimately strangles her in a moment of desperation.
Devastated and in tears, Josh calls Harmon to share the horrifying news that Dena is dead. Harmon instructs him to vanish and sever all ties, urging Josh to destroy his phone. In a bid to escape his entangled past, Josh seeks solace by applying for a job at a camping supplies store, hoping to start anew.
