In 1982, a Soviet moon lander crashes into the icy waters of the Bering Sea, setting a quiet, haunting precedent for what follows. By 2015, biology professor Stephen, [Matt Winston], joins graduate students Ronelle, [Giovonnie Samuels], and Sadie, [Camille Balsamo], on an experimental voyage to study how the warming oceans are affecting whale populations. Sadie’s grandfather Graff, [Lance Henriksen], steers them out to sea on his weathered fishing trawler Harbinger, a rugged vessel manned by Bowman, Roland, Big G, Dock, Svetlana and Atka, each with their own rough-edged routine and unspoken loyalty to the sea.
That night, a strange hum and a faint sonar ping pull Sadie from sleep. She wakes the crew, takes control of the sonar, and, with the help of the others, discovers something buried in the ice—the crashed lander, preserved by frost. Inside, a cosmonaut lies dead from an unknown infection, and Sadie salvages a skin sample for study, sparking a silent tension among the group. Stephen immediately asserts ownership of the discovery, sparking a tense dispute that Graff tries to quell, insisting that the lander belongs to Sadie. The argument sharpens the sense that something larger and more dangerous may be lurking beneath the ice.
As the crew debates the lander’s fate, Bowman urges Sadie to press forward with a closer inspection. While Big G distracts Stephen, Sadie examines the craft and uncovers a startling find: the lander was carrying tardigrades, tiny creatures famed for their resilience. The microscopic hitchhikers survive in extreme conditions, and Sadie’s analysis reveals a hidden truth—the tardigrades have undergone mutation due to cosmic radiation, granting them the shocking ability to shapeshift. The moment reframes the mission from a simple scientific grab to a high-stakes encounter with an alien-like biology that could redefine life itself.
The cosmonaut’s body vanishes, and Stephen becomes exposed to the tardigrades through careless handling, igniting a chain of terrifying events. He locks into a fevered, dangerous state, stripping down in the subzero air as the crew tries to pull him back inside. The ship’s interior grows perilous as organisms sprout from his back, spraying a dark, alien liquid over the deck. Sadie confirms the alarming possibility that they are all contaminated, and the crew resorts to liquid nitrogen to freeze Stephen and the lander in a bid to halt the spread.
As Dock shows early signs of infection, Svetlana, who is later revealed to be a Russian spy, isolates Dock in a cage and contemplates incineration. The plan is challenged when Dock itself sprouts tentacle-like growths, and the ship’s power falters, plunging them into a race against a failing backup battery. The organism’s advance is brutal and swift: it kills Atka and reveals Svetlana’s true allegiance, tightening the noose around Sadie, Bowman, Big G, Ronelle, and Graff as the mutant entity asserts control aboard the Harbinger.
With Svetlana at gunpoint, Svetlana’s spy plot unravels as she explains that the tardigrades were part of a Soviet experiment to engineer radiation-resistant cosmonauts. Her intention is to sink the boat after she boards a nearby submarine, a plan that would let the organism finish its work undisturbed. The revelation comes too late, however, as the creature lashes out, dragging Ronelle and Svetlana away into the dark beneath the deck.
Graff, Sadie, Bowman, and Big G scramble for explosive charges Svetlana has hidden throughout the ship. The last four charges lie in the bilge, a cramped space that only Sadie can access. While Sadie collects the charges, the others discover the tardigrades have consumed and absorbed their latest catch—two tons of crab—filling the ship with a heavy, fishy scent of doom. Realizing she is surrounded by the ever-growing swarm, Sadie escapes just in time, but Graff is infected in the process. He directs Big G to restart the boat and to keep Sadie safe as he hands Bowman the grim task of ending his life if necessary.
Big G makes a valiant, doomed stand to restart the Harbinger, only to be cut down by the mutated Svetlana as she fights for control of the ship. Bowman lunges to freeze Graff with liquid nitrogen, but the creature erupts through the deck, forcing Sadie to improvise a desperate escape. Graff, mortally wounded and resolute, instructs Sadie to scuttle the vessel and save herself. She pilots the Harbinger toward a looming iceberg, the ship groaning under pressure as the creature bursts onto the deck behind her.
With a portable radio crackling with the distant voice of the US Coast Guard, Sadie hears a rescue helicopter closing in. She fights to keep consciousness as the Harbinger tilts toward the cold, bright glare of the ice, the mutating horror still pursuing from the depths. The helicopter’s rotor wash finally reaches the scene as Sadie collapses on the ice, the Harbinger’s ominous silhouette fading into the spray and snow, leaving only the promise of rescue in the pale, stunned dawn.
