Mr. Trent (Robert Culp) is a man with a mission... but he doesn't know what it is, or anything else about himself. As he reflects in an Internal Monologue:
Trent is constantly pursued by sinister men in strange uniforms. He manages to stay one step ahead of them by following the advice of... his hand! Made of glass and apparently capable of speech, Trent's hand is a computer that can answer many of his questions. But it cannot tell him who he is or why his enemies seek him until he finds all of its fingers, which are lobes of the computer, and which contain the information that will explain everything. The only trouble is, the missing fingers are in the hands of Trent's enemies.
Trent captures one of his opponents, Breech (Steve Harris), and interrogates him. Breech explains that he and his companions are aliens from the planet Kyba, which is at war with Earth in 2964—1,000 years in the future. Trent, "the last man on the Earth of the future", used a "Time Mirror" to escape to 1964 in a last-ditch attempt to save humanity, and a squad of Kyben were "altered to look like humans" to go after him. They're also competing with Trent to complete the glass hand because they too need its knowledge. The Time Mirror is hidden in The Dixon Building, a dilapidated office complex; both Trent and the Kyben are wearing medallions that work as "focusing elements for the mirror", and if a medallion is removed, its wearer suddenly returns to his native time—dead. Upon hearing this, Trent removes Breech's medallion and heads for the Dixon building.
Demon With a Glass Trope:
- Absurdly Huge Population: Briefly mentioned during Trent's exchange with Arch.Trent: What is it you want? What?
Arch: I want the 70 billion future earthmen—and you know where they are!
- Alien Invasion: We never see it, but the Kyben's attempt to conquer future Earth is the basis of the plot. Trent's battle in the past is a decisive battle in the conflict.
- Aliens Speaking English: The Kyben do.
- Amnesiac Hero: Trent arrives in the past with no memories or sense of identity.
- Artificial Limbs: Trent's computer hand. Subverted when he is revealed to be a robot altogether.
- Bittersweet Ending: Trent defeats the enemy but has to hide amongst humans for a thousand years without being able to live a normal life.
- Bloodless Carnage: When Trent gets himself killed by multiple gunshots, there is no blood showing. Justified as Trent turns out to be a robot. Lampshaded by Trent himself after the Robotic Reveal:Trent: That's why, when they killed me... no bullets, no blood.
- Born as an Adult: Trent refers to himself as this during his Internal Monologue, but it's not clear if he believes it to be literally true.
- Building of Adventure: Most of the episode was filmed inside The Bradbury Building, a Los Angeles landmark dating from 1893. Harlan Ellison tailored his script around the location, which is called The Dixon Building in the episode.
- Conspicuous Gloves: Trent wears a glove over his hand, only removing it to speak to it or add a finger as he finds them.
- Covert Group with Mundane Front: One of the offices in the Dixon Building is a front for the Kyben and their time mirror.
- Death Is the Only Option: The hand tells Trent that his only option left is to get killed, so he lets the Kyben shoot him. He gets resurrected later by Consuelo.
- Defiant to the End/Dying Moment of Awesome: Two of the Kyben do this just before Trent removes their medallions.
- Breech's is nervous through most of his interrogation scene, pleading that "I can't stand pain", but he still gives Trent a kind of Badass Boast:Breech: Yes, you're vulnerable, and we'll get you. We'll have to get you finally. If you kill me, another will take my place, and if you kill him, another.
- Arch also gets such a moment. His Famous Last Words are "We'll win, Trent. In the end, we'll win."
- Breech's is nervous through most of his interrogation scene, pleading that "I can't stand pain", but he still gives Trent a kind of Badass Boast:
- Don't Look Down: Said by Trent to Consuelo while placing her outside on the ledge.
- Dramatic Necklace Removal: Used by Trent to send his enemies back into the future... fatally.
- Elevator Snare: A chase unfolds for the last finger between Trent and one of the Kyben where the former takes the stairs while the latter uses the elevator.
- Excessive Evil Eyeshadow: The Kyben have black makeup around their eyes.
- Exposition Dump: When Trent forces Breech to explain what's going on during the first act.
- Fish out of Temporal Water: Trent and the Kyben.
- Free Sample Plot Coupon: Trent must find the three missing fingers of his artificial left hand to save humanity from the Kyben invasion. Fortunately, Trent's incomplete left hand is a talking computer that can help him find the three fingers.
- Hand Gagging: Trent silences Consuelo with his hand.
- He's Dead, Jim: One Kyben declares Trent dead simply by looking at him on the floor.
- It's Not You, It's My Enemies: Explained by Trent when rejecting Consuelo's affection:Trent: Consuelo, they're not human. They'll walk over anything to get to me, destroy anything that's close to me.
- Just a Machine: Consuelo's reaction to the Robotic Reveal at the end.
- Killing in Self-Defense: Trent does this to the Kyben throughout the episode. At one point he agonizes about it: "To save all of man, I have to become a killer."
- Mr. Exposition: Breech and Trent's computer hand share this function.
- Portal to the Past: The Time Mirror.
- Railing Kill: One of the Kyben Mooks gets shot by Trent and falls over a banister to his death.
- Robotic Reveal: Trent turns out to be a robot constructed to host the human race encoded on a wire inside his body.
- Secret Passage: Consuelo knows about a hidden door that leads to the basement.
- The Short War: Arch boasts to Trent that "One thousand years in the future, we conquered your planet in nineteen days!"
- The Slow Path: Trent's fate.
- Tap on the Head: The Kyben as well as Trent go out lightly during combat.
- Terminator Twosome: The Kyben follow Trent into the past.
- Time Travel: Trent and the Kyben use a Time Machine called a "Time Mirror" for their one-way trips into the past.
- Token Romance: The romance subplot between Consuelo and Trent feels tagged on for the purpose of making the Robotic Reveal more dramatic.
- Weaksauce Weakness: The Time Mirror medallions, a weakness shared by both Trent and the Kyben.