Summaries

Synopsis

Three years before the events of the film, mysterious apex predators known as Reapers emerged from sinkholes underground, exterminating most of humanity. The survivors now live in isolated communities situated 8,000 feet or more above sea level-altitudes that the creatures do not reach.

One such community is Lost Gulch Refuge in the Front Range of Colorado, where a single father named Will resides with his son, Hunter, who suffers from a lung disease. Will is haunted by the memory of his wife, Tara, who was killed by Reapers during an expedition with Nina, a former scientist, to identify the creatures' weaknesses. After months of isolation, Hunter grows increasingly frustrated; neighboring communities have turned off their radios to conserve electricity and now communicate using flags. Will discovers that he is running low on oxygen filters for Hunter. Despite Nina's warnings, Will convinces her to accompany him on a journey to Boulder, Colorado, in search of more filters and a way to kill the Reapers.

Katie joins them, and they enter the Elba Fire Road, which leads to a mine beyond the safety line. Nina carries a compass device she invented that detects nearby Reapers due to their high bio electromagnetic pulses. Along the way, they gather supplies, including a grenade launcher, and follow the road to a former ski area. They are spotted by a Reaper, but Will manages to activate the ski lift's backup generators, allowing the group to narrowly escape to a location above the safety line. They rest at an old lodge, where Nina theorizes that the Reapers do not eat or sleep, suggesting they are not biological creatures.

The following morning, the group arrives at a former mining tunnel familiar to Will from his time as a miner; however, the lower levels of the mines extend below the safety line. If they enter, Nina's compass will not function underground. As they descend into the mines, they discover that the level above the safety line has been welded shut during the initial invasion, forcing them into the lower levels. Soon after, they are attacked by a Reaper, which kills Katie with its tendrils. Nina and Will manage to escape and return to the surface.

Nina proposes turning back to her lab for her stockpile of magnesium. She hypothesizes that the Reapers' impenetrable scales have magnetic defensive mechanisms and that bullets laced with magnesium could penetrate and kill the creatures through internal combustion. They continue on to Boulder and successfully locate oxygen filters in an abandoned hospital. A Reaper attacks them, but Will shoots gas canisters to stall it, providing enough time for their escape. Although Will is eager to return to Hunter, Nina persuades him to help her get back to her former lab at the U.S. Department of Energy. During their time together, Will learns that Nina lost her family in a Reaper attack. She allows him to return to his son while she continues her research on how to defeat the creatures. After several attempts, Nina successfully kills a Reaper that breaks into her lab using a bullet laced with cobalt.

Will departs in a pickup truck, but the tires pop, forcing him to flee toward the safety line while being pursued by Reapers. They corner him, but Nina arrives just in time and uses her cobalt-laced bullets to destroy them, causing them to explode from internal combustion upon impact. They realize that the Reapers are not biological entities but rather machines made from advanced alien technology, confirming Nina's theory.

They return to Lost Gulch, where Will is reunited with Hunter. Nina raises a pirate flag to signal the nearby communities in the Rocky Mountains, indicating that a Reaper has been killed. The communities resume radio communication and start arming themselves with cobalt-coated bullets to fight back against the Reapers.

In a post-credit scene, Nina looks through a telescope with Will by her side as three greenish "meteorites" enter orbit.