Harbinger

In 1982, a Soviet moon lander plunges into the icy waters of the Bering Sea, vanishing beneath the waves. The wreck carries a mysterious cargo that will echo across decades. The crash seeds the hidden mystery that drives later events.

In 2015, biology professor Stephen and graduate students Ronelle and Sadie board the fishing trawler Harbinger to study whales amid warming seas. They sail with a crew including Bowman, Roland, Big G, Dock, Svetlana, and Atka. What begins as a routine research voyage soon becomes entangled with rivalries and secrets.

One night Sadie wakes to unusual activity and uses the sonar to locate an anomaly beneath the ice. With the crew's help, she retrieves a Soviet lander encased in ice from the surrounding water. Inside, the cosmonaut is dead from an unknown infection, and Sadie takes a skin sample for analysis.

Stephen immediately claims ownership of the lander, but Graff disputes the claim and says it belongs to Sadie. The argument exposes rivalries that threaten the mission's credibility and put the crew at odds. The discovery's value eclipses personal interests and raises ethical questions about possession of extraterrestrial relics.

Sadie analyzes the lander and learns it carried tardigrades, hardy micro-creatures that can survive extreme conditions. Cosmic radiation has mutated them, giving the organisms the ability to shapeshift and move between hosts. The revelation signals a new, invisible threat aboard the Harbinger.

The cosmonaut's body goes missing after the initial retrieval, and Stephen begins investigating the wreck. He becomes contaminated with tardigrades, while the reanimated cosmonaut's body kills Roland. The crew realizes the danger is biological as well as scientific.

Stephen experiences a chilling collapse of discipline as he strips on deck in sub-zero air. The others intervene and, in a desperate bid to contain the outbreak, freeze Stephen's body and the lander with liquid nitrogen. The outbreak shifts from discovery to an active threat aboard the vessel.

Dock shows signs of infection, and Svetlana locks him in a cage while planning to incinerate him to stop the spread. The crew objects, but Dock sprouts tentacle-like growths, confirming the organism's reach. A power cut and a struggling backup battery heighten the peril aboard.

Svetlana is revealed to be a Russian spy, aligning the tardigrade threat with a Soviet experiment to create radiation-resistant cosmonauts. She intends to sink the boat after boarding a nearby submarine, turning the crisis into a planned betrayal. The survivors brace for a final, deadly confrontation.

The tardigrade organism attacks, dragging Ronelle and Svetlana away into its mass. The crew fights to contain the outbreak as containment fails and the ship devolves into a life-or-death struggle. The safety of the survivors hinges on rapid, decisive action.

Graff, Sadie, Bowman, and Big G scour the boat for Svetlana's hidden explosive charges; four charges are hidden throughout the bilge and other compartments. Sadie, with unique access to the bilge, collects the charges for potential use in detouring the threat or escaping. The team uses the moment to prepare for a perilous exit or detonation.

The tardigrades have consumed two tons of crab and spread through the ship, turning the Harbinger into a moving hive. Sadie realizes she is standing inside the mass and must flee to avoid being consumed. Graff becomes infected, prompting Big G to restart the vessel to buy time and preserve a chance of escape.

Big G restarts the ship but is killed by the mutated Svetlana. The creature then impales Bowman as the crew scrambles to regain control. Graff pleads with Sadie to scuttle the boat and save herself, sealing the ship's doomed, desperate pivot.

Sadie steers the Harbinger toward an iceberg, risking everything to escape the creature's grasp. A rescue helicopter approaches as Sadie collapses on the ice, motionless, with the Coast Guard closing in for a desperate recovery. The final image hints at a fragile survival against the odds.