In the year 2065, Earth faces a grim reality as it is overrun by alien entities known as Phantoms. These creatures first appeared 34 years ago, and they are deadly; upon physical contact, they drain the Gaia spirit from living beings, instantly killing them. Those who survive have retreated to "barrier cities" fortified by energy shields that fend off these menacing invaders, as they continue their desperate fight for liberation.
Amidst this chaos, scientist Dr. Aki Ross (played by [Ming-Na]) finds herself infected by a Phantom during an experimental venture. Together with her mentor Dr. Sid (portrayed by Donald Sutherland), they embark on a mission to save humanity by identifying eight unique spirits—energy patterns intrinsic to various life forms. When combined, these spirits generate a powerful wave capable of obliterating the Phantoms.
While searching for the sixth spirit in the desolate remains of New York City, Aki is cornered by Phantoms. Fortunately, she is rescued by Captain Gray Edwards ([Alec Baldwin]) and his elite squad, Deep Eyes, which includes Master Sergeant Ryan Whittaker (Ving Rhames), Neil Fleming ([Steve Buscemi]), and Corporal Jane Proudfoot (Peri Gilpin). It soon becomes evident that Gray shares a romantic history with Aki, complicating their mission.
Upon their return to Barrier City #42, the squad undergoes medical scans, revealing that Gray has also been infected. In a bold move, Aki decides to treat him within the city, utilizing lasers to eliminate the parasite before it can spread. Meanwhile, Dr. Sid arrives, permitting Aki to bypass further scans, as he unveils that 20 years prior, he discovered an energy signature linked to the Phantoms. He is the mastermind behind the technology being employed to combat these beings and has been collecting the eight spirits believed to stem from Gaia, the planet’s life force.
Back in her barrier city, Aki joins Sid in front of the leadership council, along with General Douglas Hein (James Woods). Hein, adamant about using the Zeus cannon—a formidable weapon stationed in orbit—to eradicate the Phantoms, raises concerns in Sid about the cannon's potential to damage the Earth's Gaia spirit. Sid warns that aggressive attacks on Leonid, the meteor where the Phantoms nest, only drive them deeper underground, suggesting that escalating firepower could be catastrophic.
To delay the cannon's deployment, Aki reveals her infection, claiming that the gathered spirits stabilize her condition, persuading the council to consider alternative strategies against the Phantoms. The six spirits they’ve collected thus far include: Human, Fish, Sparrow, Deer, a dying little girl in the emergency room, and a Plant. However, this revelation leads Hein to mistakenly suspect Aki is under Phantom control, subsequently assigning Gray to monitor her closely.
As Aki's health deteriorates and she slips into unconsciousness, the team manages to locate the seventh spirit. The Phantoms are drawn to Aki’s unique energy signature, putting her life at risk. Gray intervenes to protect her from his own team, who would have shot her in fear. Aki has a dream that reveals the Phantoms to be the lost spirits of extraterrestrials, victims of a long-ago civil war that obliterated their world and transformed them into Phantoms.
In a drastic move to compel the council to authorize the Zeus cannon's firing, Hein lowers part of the barrier, accidentally allowing a horde of Phantoms to invade the city. Aki, Sid, and the Deep Eyes crew scramble to Aki’s ship for escape, but tragically, Ryan, Neil, and Jane lose their lives in the fray. With courage as his guide, Ryan creates a distraction to protect Aki, allowing her and Gray a chance to escape. Their harrowing escape culminates in a sweet yet bittersweet kiss between Aki and Gray.
Meanwhile, Hein manages to board the Zeus cannon's space station just as he receives the green light for a strike. Sid embarks on a perilous mission to uncover the eighth spirit at the alien astro-impact crater. As he prepares to attract the spirit using a device on Aki, Hein recklessly fires the Zeus cannon into the crater, obliterating the eighth spirit and unveiling the Phantom Gaia, despite Aki's desperate attempts to explain that the Phantoms are merely lost souls, not aggressors.
In a transcendent moment, Aki connects with the Phantom home planet and absorbs the eighth spirit within herself. When she awakens, she combines it with the other seven spirits, while Hein, ignoring the warnings of impending destruction, continues to unleash the power of the Zeus cannon, ultimately leading to his own demise.
With Gray sacrificing himself as the conduit needed to transfer the revitalized spirit to the alien Gaia, harmony is restored to Earth as the Phantoms ascend into the cosmos, no longer a threat. Aki is rescued from the crater, cradling Gray’s lifeless body, gazing into a world reborn, freed from the grasp of despair.
