After three months of recording in Greenland, Lea, a marine microphone operator, returns to Lindisfarne. She first visits the house of a friend to pick up her son Peter, who—in his mother’s absence—has been performing worse at school and ran away on September 14th to go find Lea. Unsettled by his disappearance on the same day she had gone on a fateful dive, Lea takes him home. However, once Peter falls asleep, Lea turns all her attention to her recordings, backing them up and listening to them to ensure their safety. She bundles herself in a blanket as she does so, curiously cold in a house that should be warm. She finally reaches the most recent track, recalling how her fellow team members regarded her as a killjoy obsessed with the work of the expedition, as well as how her producer Nils had been so apprehensive about her enthusiasm for the recording even after the mysteriously tragic events of the dive. Nevertheless, she plays the track, musing it is her best work yet.

As the track plays, she begins remembering the details of the dive. Beforehand, the team’s Inuit guide fell ill, squeezing his hands to his ears and complaining of a loud noise. He told the team he felt this way whenever the eqalussuaq, or Greenland shark, came close. Excited at the prospect of filming the elusive shark, the team heads for the water, with Lea boarding the truck the fastest. Breaking from the memory, Lea calls Nils to ask him for the footage of the dive. When he answers, he’s despondent, telling Lea he could have lost her the same way he lost Reeta, the second camerawoman. Unfazed, Lea requests he send her the footage. She remembers how Reeta volunteered to dive after the team couldn’t spot the shark from the water’s surface. She also remembers how she volunteered to go with her, hoping to record audio of the creature. Lea syncs the audio with the video and watches herself dive underwater. She sees the shark appear, moving quickly towards her. On screen, she panics, and although the audio is incoherent to the average viewer, she hears herself scream for the shark to take Reeta instead. As the shark changes course for Reeta, it releases a loud scream, startling Lea.

The next day, Lea walks the shores of Lindisfarne, recording its sounds to send to a record label for ambient music. Suddenly, she hears a shriek coming from the ocean. Later, she and Peter eat at a McDonald’s, waiting for the tides to turn. Sullen, Peter complains of how she left him, but Lea attempts to reassure him that she will always return to him—despite recognizing how little she thought of him during the expedition. That night, she leaves a small radio in his room to lull him to sleep. In the morning, the house pulses with a shrieking noise, emitting a scream from every speaker embedded in the television, radio, and computer. Lea checks her audio files, but they have all been replaced with the screaming. Horrified at the loss of her work, she unplugs her devices, but the scream continues. She begs for it to leave her alone, and it does. Her recordings reappear. However, the sound begins to afflict only Peter. Understanding the sound means for her to choose between her son and her work, Lea reluctantly chooses to save Peter, deleting the files and smashing the computer’s hard drive. Still unsatisfied, the scream manifests in Lea, causing her to feel immense pain. It leaves her with tinnitus, as well as a scar reminiscent of the tearing motions the Greenland shark does to its prey.