As the Jupiter 2 continues on its journey through space, it suddenly begins to accelerate out of control and passes the speed of light. The entire crew passes out and when they awaken, they find that they are in their own solar system. The planet Earth is in sight, and the Robinsons happily land on it.
John tries to raise Alpha Control but is unable to do so on any frequency. Wanting to look around, the Robinsons emerge from their ship to see where they are. After a brief exploration, they come to the startling conclusion that though they are indeed on Earth, they have somehow arrived on Earth in the year 1947.
The townspeople who live nearby have observed the landing on the Jupiter 2 and believe it to be a hostile alien ship. After they encounter the Robot, they are certain that they have been beset by visitors from another world. The townspeople form a vigilante group, determined to destroy the invaders.
Although John has ordered everyone to stay on the Jupiter 2 until they leave in the morning, Dr. Smith sneaks off. He figures Earth is Earth, no matter what year it is, and that he may even be able to use his knowledge of the future to make himself a rich and powerful man. He sneaks into town and disguises himself as the fire chief from a neighbouring town. Will and the Robot follow him but are soon captured by the vigilantes.
Will and Robot are locked up in a barn and Dr. Smith refuses to set them free. He wants to stay on Earth but he doesn’t want to do so alone. He thinks that by holding Will “hostage” he can force the Robinsons to stay on Earth as well. When John finds out Will is being held prisoner by the townspeople, he insists they let his son go, or else he will blast them with lasers.
Smith takes control of the vigilantes and convinces them that they can destroy the Jupiter 2 with a historical cannon on display in the town square. He also tries over and over again to persuade the Robinsons to surrender and agree to live on Earth, but they refuse. Since Smith is too scared to stay on his own, he orders the townsfolk to fire the cannon at the Jupiter 2.
Will makes friends with a local girl called Stacy who eventually decides he is harmless and helps him and the Robot escape from the barn. They rush to the Jupiter 2, which has not suffered damage from the cannon attack. John orders everyone on board and they prepare to lift off. Too frightened to be left behind on his own, Dr. Smith changes his mind about staying on Earth and screams, rushing onto the ship as well. The Jupiter 2 blasts off for outer space, leaving the confused townspeople behind to wonder.
- This is one appearance of the full-size Jupiter 2 mock-up. The other is The Derelict. Parts of it are also seen in The Ghost Planet.
- The buildings around the full size mock up of the Jupiter 2 are the sound stages at 20th Century Fox (Fox Studios)
- When the ship experiences runaway acceleration during the teaser (up to and in excess of he speed of light) the outside starfield doesn't change in appearance. There should be some Doppler shifting of the starlight. Also the Jupiter 2 is shown twisting and spinning through a cloud of red gas, a shot reused from "Blast Off Into Space."
- This is the final appearance of Debbie the Bloop (disappearing behind a folding door in the teaser). She would go on to be seen in the television series Daktari.
- The Robinsons' decision to change out of their fatigues and into their silver uniforms just before landing helped to confuse the locals in rural Michigan into believing that they are aliens.
- One of the businesses at the lumber yard is the "West End Cabinet Company".
- Apparently the Robinson's accidental arrival in the United States in 1947 caused the term "flying saucer" to become part of the lexicon.
- All of the electrical power around the town fails due to the Jupiter 2's landing. This doesn't happen in the pilot during take-off so supposedly Alpha Control is EMI shielded. However the phone in the lumber yard rings a second after the Jupiter 2 takes off so perhaps there is no effect during take-off.
- The car found in the lumber mill appears to be a 1942 Chevrolet. It has the GM badge removed for legal reasons. The radio appears to be genuine original factory equipment.
- The townspeople suffer no ill effects from the take-off of the Jupiter 2 despite being within a few dozen yards of it when it does. This is in contrast to the Robot's statement in "Time Merchant" where he claims he will be incinerated by being so close to the ship when it departs the launch pad.
- The name of the town is "Manitou Junction", but at the end of the episode Craig refers to it as "Manitou Falls" during a phone conversation. There is an actual Great Manitou Falls in northern Wisconsin near Lake Superior, so perhaps the town's location is the Upper Penisula of Michigan.
- Smith tells the Captain that they're headed towards "Target:Jupiter" despite none of the townspeople ever being told what the ship is actually called. Nor do they question where he got that knowledge.
- In other episodes the Jupiter 2 can safely withstand bombardment of meteors travelling at thousands of miles per hour but here a 40 lb. cannonball travelling roughly at the speed of sound apparently is strong enough to damage it irreparably.
- October 17th, 1947 was a Friday, not a Saturday as indicated in the script. It was also the birthday of Michael McKean, perhaps best known as a member of Spinal Tap.
- Manitou Junction appears to have two cannons - Stacy tells Will they took the one from the town square to blow up the ship but then there's another one seen right across the street from the fire station when they escape from the barn.
- Maureen barely recognizes the rotary dial telephone at the lumber yard, but in The Reluctant Stowaway there are many rotary dial telephones at Alpha Control Headquarters.
- Whether and how the Robinsons make it back to their own time is never explained. But they apparently do as evidenced by where the ship lands in "Target:Earth."
- What was with the goofy music throughout this episode? It’s hard for there to be any kind of real tension when the soundtrack is so cartoonish.When the Jupiter 2 passes through the time rift, everyone passes out. Smith is the first to wake, and he starts moaning and crying, thinking all the others are dead. What kind of a medical doctor can’t even tell when people are alive or dead?
- Smith is unable to calculate the answer to the question of 50 minus 3. Apparently the doctor has become so stupid at this point in the series he can’t do simple math.