A man, Trent, runs through the night in the city of Los Angeles. He has no memory of who he is or where he is, and believes that the people that wiped his memory are pursuing him. Trent escapes them once and takes refuge in an alleyway, and removes the glove on his left hand. Beneath it is a glass hand containing a computer. The computer can’t tell him who is following him, but explains that each pursuer wears a medallion. They have traveled to the present from the future using a Time Mirror, and can send more of them. It tells Trent that it can serve him better if it’s complete, and is missing three finger nodes.
An alien pursuer closes in on Trent, who ambushes it. He pulls the medallion off of its neck and it disappears. Another alien closes in and finds the discarded medallion, and Trent grabs its medallion. He then straps the alien, Breech, to a gate. The alien admits that it can’t stand pain, and explains its race is the Kyben, and they’ve been altered to look like humans so they could come back to find Trent. When Trent asks why, the Kyben explains that they are at war and came to find his hand, which holds all knowledge. All the Kyben was told was that they have the three fingers, and Trent was the last man from Earth. Trent asks Breech about the medallion, and the Kyben explains that it holds them in the present. If it’s removed, they “snap” back to the future. Trent notes that it is wearing one as well, and the Kyben swears that they will get him eventually. However, Trent forces Breech to explain that the Time Mirror is at the Dixon Building in downtown, and then removes the medallion, sending the Kyben back.
Trent makes his way through the sewers to the Dixon Building, while his hand informs him that he came from a thousand years in the future. Earth of that time had no defense against the Kyben, who conquered the planet in a month. However, every man, woman, and child, 70 billion people, disappeared overnight, leaving Trent. The vanished Earthmen gave Trent the glass hand, and Trent stole a medallion and made his way to the 20th century. It repeats that Trent has to get the three lobes of its computer brain, and when united they will reveal why Trent is the last man on Earth. Trent must seek out the Time Mirror to eliminate the Kyben’s ability to travel back and find him.
Coming up from the sewers, Trent enters the building. The computer explains that the building is now part of a slum, and one of the offices is a front for the Kyben. The Kyben leader, Arch, calls out and explains that Breech was under orders to lure Trent there. The Kyben have surrounded the building with an invisible force field, and call upon Trent to surrender in return for his life. Trent asks the glass hand where the 70 billion people are, and it explains that they are hiding and Trent is the key to their release. However, it can’t tell him how unless it is made complete.
A Kyben opens fire on Trent from above, and Trent shoots and kills it. He ducks into a ladies apparel office, C & E Biros Apparel, and turns on the light to reveal a woman cowering in the corner. She insists that she has nothing and begs Trent to spare her. Trent grabs her when two of the Kyben pass by. He explains to the woman that they want to kill him and he needs her help. Trent asks her to remain quiet and releases her, and they hide as one of the Kyben comes in. Once its back is turned, Trent knocks it out. He then explains to the woman, Consuelo Biros, that they are aliens from the future. To prove what he says, Trent rips off the Kyben’s medallion, causing it to vanish. Consuelo accepts what he is saying but says that she was working late as a cleaning lady and wants to leave. Trent warns that she can’t leave due to the force field, and he has to find the Time Mirror and destroy it. She suggests that he hide in the basement and shows him a blocked door.
Another Kyben, Battle, finds them and Trent quickly knocks him out. He prepares to kill it, and Consuelo wonders if he has to kill it. Trent says that it’s gone too far for anything else and asks why she dislikes violence. Consuelo explains that she and her husband Esteban owned the office and he beat her. She asks again if Trent has to kill it, and he interrogates the Kyben when it wakes up. Battle insists that it’s not afraid to die, and that it’s a patriot. Trent asks where the other three parts of the hand’s brain are, and Battle says that there is one piece in the present and two in the future. Arch has the one in the present, and Vaughn and Durn have the two in the future. Consuelo asks Trent to spare Battle, and it takes advantage of the distraction to break free, run to the door, and yell an alarm.
Trent and Consuelo flee into the building and Trent tells the hand what has happened. It suggests that Trent let the Kyben kill him. He covers the hand back over and then steps out. The Kyben quickly gun him down and he collapses. Arch confirms that he’s dead and attaches his finger node to the glass hand. He informs the others that Durn and Vaughn will soon arrive with the other two fingers and they’ll be able to learn where future humanity is hiding.
The Kyben take Consuelo and Trent’s corpse back to the office. Arch doesn’t know who Consuelo is and wants to hold her for interrogation, and speculates that once they complete the hand, it can provide them with a way to safely return to their own time. Once they’re alone, Consuelo prays to the Virgin Mary for help. The glass hand activates and tells Consuelo that she can save herself. It directs her to get a moist cloth and confirms that Trent is dead. Once she has the cloth, the hand tells her to apply the cloth to three key spots. Trent comes back to life and his temperature soars. The hand directs Consuelo to remove the cloth, and Trent opens his eyes. Consuelo tells him what happens and Trent confirms that there is no blood and no bullet holes. He wonders what the glass hand can do with all three parts if it raises the dead with just one.
Consuelo tells him that Durn and Vaughn are coming, and Trent asks the hand what to do. It extrapolates that the Kyben can use the hand to learn where the humans are, and how they can either return to their own time or permanently survive in the present. However, it needs the second lobe to tell Trent where humanity is hiding. The hand detects an energy drain, confirming that Durn has come through the Time Mirror. Trent grabs Consuelo and they go up the stairs. Durn spots Trent and knocks him out, and Consuelo reluctantly snatches off the medallion rather than let it kill Trent. It drops the second finger as it disappears, and Trent finds it when he wakes up.
Trent takes Consuelo to the attic to hide. He opens a window and confirms that the force field is still active. When Trent tries to get Consuelo out onto the roof, she’s unable to go out due to her fear of heights. She faints and Trent finds the medallion in her hand. He then inserts the second finger and the glass hand tells him that the Earthlings unleashed a radioactive plague, knowing it would destroy all intelligent life including themselves. To survive until the plague dissipated, they used a device to translate all 70 billion people into electrical impulses and stored on a strand of gold-copper wire. As Consuelo wakes up, the glass hand explains that the wire was entrusted to Trent, but it can’t say where until it’s complete.
Arch receives word that Vaughn is coming through the mirror with the third and final piece.
Consuelo asks Trent how long it’s been since he slept, and he admits that he doesn’t seem to grow tired. He wants to get her out given the danger, but she isn’t afraid despite the risk. Consuelo admits that she’s fallen in love with him, and Trent says that he can’t return the feeling. She knows but says that it doesn’t matter as long as one of them loves, and leans forward to kiss him. Trent turns away before she can and tells her to hide on the roof. Consuelo reluctantly goes outside and Trent goes to defeat the Kyben.
Trent ambushes Arch and uses the Kyben’s medallion to force it to reveal where the Time Mirror is hidden. Cowed, Arch directs him to their cover office, and says that his people will win because Trent is the last human. Trent pulls off the medallion as the other Kyben call for Arch. Trent perfectly impersonates Arch’s voice, and the Kyben call out that Vaughn is coming and there’s trouble in the future. Trent goes to the office and slips into the outer room. Budge comes through and says that its comrade, Vaughn, is coming next. It informs the others that as soon as Trent escaped through the mirror, a plague started killing the Kyben. Budge came through to protect Vaughn and recover the hand so they could stop the plague.
Vaughn comes through with the third piece and Budge grabs it immediately. Trent breaks in, rips the medallions off of two of the Kyben, and shoots the Time Mirror. While he struggles with Budge, another Kyben soldier grabs the finger, runs outside, and throws it down a mail slot. The Kyben stuns Trent and takes the elevator down, and Trent leaps down the stairs to get to the mail box first. He shoots the box open and knocks out the last Kyben as he arrives in the elevator. Another Kyben opens fire but Trent makes it to the attic and hides. The remaining two Kyben enter as Trent hides in the rafters and inserts the third finger. He jumps down and knocks out one, and the other one grabs him. They smash through the window next to Consuelo. Begging God’s forgiveness, she rips off its medallion, saving Trent.
Back inside, Trent tells Consuelo that the Time Mirror is destroyed. He tells Consuelo to go downstairs while he disposes of the last Kyben. He then meets her in the office and asks the glass hand where humanity is hiding. It informs him that the wire holding humanity is inside of Trent’s control solenoid, protected from his circuits. When he asks what it means, it tells him to push the fingers of the hand together in the proper sequence. A panel in Trent’s chest open, revealing circuitry and the hand explains that humanity programmed Trent to believe that he’s a human, but he’s actually a robot. That was how he survived, and the glass hand was able to restore him. Trent reaches for Consuelo’s hand, but she withdraws in shock and horror and leaves without a word. Alone once more, Trent realizes that he now has twelve hundred years to wait until he “arrives” in his own time and the plague has dissipated, so that he can free humanity.