Qarlo Clobregnny (Michael Ansara) and his nameless Enemy (Allen Jaffe), two Super Soldiers from the far future, stalk each other across a barren wasteland. Voices in their helmets command them to "Find your enemy! Attack! Kill!" As they rush each other, two colliding laser beams hit near them, which somehow plunges them both into a swirling time vortex. The Enemy's fate is described by the Control Voice, in a rare mid-episode narration:
The Enemy struggles against the time warp that entraps him, which is gradually dissipating. Meanwhile, Qarlo ends up on a city street in 1964, where one of the first things he sees is an elderly news vendor opening a bundle of newspapers with a knife. Feeling threatened by the "weapon", Qarlo attacks, causing everyone around him to panic. When the police arrive, Qarlo uses his laser rifle to disintegrate a squad car — but when they grab Qarlo and remove his helmet, the soldier's super hearing is overwhelmed by the sudden onslaught of loud city sounds, which weakens him enough for the cops to capture him and take him to a holding facility.
Since no one can understand Qarlo's futuristic language, philologist Tom Kagan (Lloyd Nolan) is called in to try to make sense of him. Kagan and his colleague, government agent Paul Tanner (Tim O'Connor), examine Qarlo and gradually figure out who and what he is. Kagan realizes that Qarlo has been bred purely as a killing machine, but he believes he can reawaken the warrior's humanity (even after Qarlo briefly becomes violent with him), so he persuades a reluctant Tanner to let Qarlo live with him and his family for a while. Meanwhile, the time warp that imprisoned the Enemy finally fades away; once free, he resumes hunting Qarlo.
Qarlo becomes an unlikely house guest for Kagan, his wife Abby (Catherine MacLeod), and their children Loren (Ralph Hart) and Toni (Jill Hill). At first, Kagan seems to be making progress with Qarlo, who relates the details of the dystopian future he comes from. However, the soldier eventually decides that "Trooper needs a gun" and breaks into a gun shop, where he grabs a powerful hunting rifle. Kagan talks Qarlo down before he can shoot anyone and takes him home, although the soldier insists on keeping the weapon. Just as Qarlo decides to stay with the Kagans because they are "not enemy", the Enemy tracks him down, blasting through the wall of the Kagans' house. Qarlo fights back, and as the Kagans watch helplessly, the soldier and his Enemy zap each other into nothingness.
"Trooper needs a trope":
- Archaic Weapon for an Advanced Age: It's highly unlikely that we would still use human soldiers in combat in the far future.Kagan: Wars in the future are fought with men and animals.
- Bad Future: Qarlo comes from one, and the closing narration asks if it's possible to prevent it.
- Crowd Panic: Breaks out when Qarlo hits the streets in 1964.
- Deadpan Snarker: Paul Tanner is one of the wittiest characters in the entire series. When Kagan says he wants to talk to Qarlo in person, Tanner warns him that "[Qarlo will] take you and tear along the dotted line!" Later, when Qarlo finally attacks Kagan, Tanner asks him "How does it feel to be dribbled like a basketball?" A doctor also gets into the act, telling Kagan, "Do us both a favor. Don't let [Qarlo] bounce you around like a ping-pong ball."
- Death by Adaptation: The original short story ends with Qarlo surviving and dedicating his life to averting the Bad Future that created him.
- Death Equals Redemption/Heroic Sacrifice: Qarlo seems to sacrifice himself to save the Kagans from the Enemy, but the closing narration expresses enough doubt to make it an Ambiguous Situation.
- Diabolus ex Machina: The Enemy finds Qarlo just as he's decided to stay with the Kagans.
- Dramatic Thunder: Rolls when the enemy soldier invades the house.
- Evil-Detecting Dog: Apparently, we will use cats in the future for warfare. As Kagan explains, in Qarlo's world "Cats are used for reconnaissance, and by telepathy, they relay their messages."
- The Film of the Book: Harlan Ellison adapted the script from his 1957 short story "Soldier from Tomorrow".
- Fish out of Temporal Water: Qarlo and the Enemy wind up 1800 years in the past, although it takes the Enemy a while to complete the trip.
- Future Slang: According to Kagan, Qarlo's language is this. It often sounds like You No Take Candle, because it's slimmed down to efficient shorthand syllables, and there's about 1,800 years' worth of pronunciation drift. At first he keeps repeating "Nims qarlo clobregnny prite arem aean teaan deao", which is really his name, rank, and serial ID letters: "Name's Qarlo Clobregnny, Private, RM-EN-TN-DO".
- Hates Being Touched: Kagan is the first person ever to touch Qarlo, which causes the soldier to Freak Out. He repeatedly yells "Don't never touch me!" while physically attacking Kagan.
- Motherly Scientist: Kagan takes Qarlo under his wings, protecting him from the government's militant forces.
- Obligatory Earpiece Touch: In one scene on the battle field, Qarlo touches his helmet to better understand the "Kill, Kill" order coming in.
- Purple Is Powerful: The "ruling body" of Qarlo's future is called "The Purple".
- Shipped in Shackles: Qarlo is transported in the back of a police car, tied into two straight jackets.
- Shout-Out to Shakespeare: The Kagan family's cat is named Macbeth.
- Super Hearing: Kagan says that Qarlo's hearing is "on a much more sensitive threshold than ours", which is why his helmet has "built-in sound baffles to deaden noises". This turns into a Logical Weakness when the 1964 cops remove his helmet, suddenly exposing him to ordinary street sounds that he's not equipped to handle.
- Super Soldier: Qarlo has Super Strength and extraordinarily sensitive hearing and has been raised as a killing machine.
- Terminator Twosome: Briefly, when the Enemy finally locates Qarlo.
- You Have GOT to Be Kidding Me!: Line said by Tanner when he learns that they sent a philologist for assistance.