Meteorology student Pavel "Pasha" Danilov finds himself interning at a secluded, Soviet-era weather station on a remote Arctic island. His only companion is the grumpy and seasoned geophysicist Sergei Gulybin, with whom he shares the monotonous duty of collecting weather and tide statistics every four hours using outdated equipment. Pasha's polite demeanor is often overshadowed by his fear of Sergei, who looks down on him and harbors jealousy since Pasha can operate their only computer.
Things take a difficult turn when Sergei embarks on an unauthorized fishing trip, instructing Pasha not to disclose this to anyone. When an urgent message comes through the radio requesting Sergei, Pasha feels obliged to fabricate excuses for his absence. The situation escalates when Pasha receives heartbreaking news that Sergei's wife and young son have been "gravely injured" in an accident, though it becomes painfully clear they are deceased. He is advised to deliver this tragic news to Sergei but to "leave him alone" afterward. This somber message haunts Pasha and disrupts his work, leading him to falsify log entries that he desperately tries to cover up when Sergei returns in high spirits, recounting a heartwarming story about salted trout and his wife's pregnancy cravings.
Confrontation inevitably arises when Sergei discovers Pasha's deceit. In a fit of rage, he chastises Pasha for disrespecting the station's longstanding integrity since it has been continuously occupied since 1935. Sergei's anger is amplified by allegations that Pasha is merely a "tourist" attempting to document a trivial experience, referring mockingly to it as "How I Ended This Summer," a play on the cliché of summer vacation essays. The tension thickens as Sergei shares a chilling story about a past geophysicist whose relationship with his partner soured so badly that it ended in violence.
Consumed by fear of Sergei and deciding his best course of action is to sabotage their communication, Pasha cuts off the radio. When Sergei goes fishing again, Pasha learns that the ship intended to rescue them is trapped in ice, but a helicopter is en route before the weather deteriorates. Preparing to meet the helicopter with a rifle, Pasha's attempts are futile as the pilot cannot locate the flares due to heavy fog. In a harrowing turn of events, he finds himself in a life-threatening chase with a hungry polar bear, ultimately falling down a steep embankment.
After waking up on Sergei's boat, Pasha tries to speak with him about the devastating news he has been carrying, but is dismissed. Eventually, in a moment of desperation, Pasha reveals Sergei's family's fate, which sends him into a frenzy. Under intense stress and with an injured leg, Pasha mistakenly assumes Sergei is attacking him and fires in panic, narrowly missing. This sets off a chain reaction that drives Pasha to hide in an abandoned cabin.
As Pasha struggles for survival, he overhears Sergei outside and remains hidden in fear. Sergei's attempts to reach out to him are met with silence as Pasha inadvertently exposes himself, which alarmingly leads him to a source of radiation. In a desperate bid for sustenance, he steals fish from Sergei and almost chokes on a bone, his anger towards Sergei boiling over. In a twist of fate, they find themselves in a dire situation involving contaminated fish. When Sergei invites Pasha to share a meal, reality comes crashing down as Pasha reveals the contamination, prompting a horrific moment when Sergei realizes the truth.
With the arrival of the rescue ship, The Academic, Sergei surprises Pasha by expressing a desire to remain on the island, leading to a tense standoff where Pasha threatens to divulge the events that transpired, hoping to force Sergei to seek medical assistance. Sergei's insistence on solitude culminates in a chilling embrace, leaving Pasha questioning the fine line between survival and madness in the frigid isolation of the Arctic.
