"Invaders from the Fifth Dimension"

Invaders from the fifth dimension

LiS episode
1x08 / 8th of 83 aired
Production #
First aired
Watch online now
Written by
Directed by
Previous episode
Next episode

Last week, you recall, we left Doctor Smith with Will Robinson, both unaware that their every move was being scrutinized from afar, by weird alien eyes...


Luminous aliens capture Dr. Smith, and plan to replace their burnt-out computer with his brain. However, he bargains with them, and promises them Will's brain instead. They release Smith but with a ring around his neck as a disciplinary tool.

Smith tricks Will into accompanying him and, while keeping Will from responding to a frantically-searching father, leads Will to the aliens. Meanwhile, Maureen has spotted the alien ship just as it was fading from view and she, Prof. Robinson, and the Robot then search for them in the Chariot.

After Will is captured, Smith hurries to the chariot and leads them to the aliens. There is a stand-off, but when the aliens realize that Will's emotional distress about leaving his family will destroy their ship, they release Will, forsaking his help to calculate their journey home.

Background InformationEdit

  • When the sparks start to fly out of the alien spaceship's electrical components at the end of the episode, it becomes apparent that the alien spaceship does not have any fuses or circuit breakers in it. Just like the Jupiter 2.
  • It is possible that this episode may have been used to "kill off" Dr. Smith had the decision not been made to keep him as a permanent cast member.
  • The aliens seen here are based upon the bubble-headed alien seen in the last moments in the Pilot episode. They have been modified to have no mouths and wear long flowing robes, greatly improving their sinister appearance.
  • This episode marks the first time Dr Smith attempts to save his own life by trading that of a Robinson (usually Will or Penny).
  • When Smith suggests he get computers from the Jupiter 2 for the aliens, they dismiss the use of such "primitive toys" as "a million times a million of them" would still not meet their needs. The Jupiter 2's computers are Burroughs B205s, which could execute operations at kilohertz frequencies. Current microprocessors of course operate at gigahertz frequencies or about a million times faster than the B205.
  • Don flies the Jetpack in this episode. He will do it again in "The Raft".
  • The aliens' spaceship is perhaps the most original design of the series. Apparently lacking rocket motors or other conventional means of propulsion it looks truly non-human. Perhaps that's why it was not reused in the series as so many other props and models were.
  • During the final scene, as the Robot is seen walking among the rocks near the alien spaceship, Bob May's legs can be seen sticking out of the bottom of the Robot's costume.
  • This episode is the first in which Smith remarks "The pain, oh the pain!"
  • Maureen Robinson drives the chariot in this episode.
  • In one scene with Will and Dr. Smith, there are stalagmites among the large rocks in a desert like setting. Normally associated with dissolved limestone in a cave or lava tube formation in a volcano here on Earth. With Will being a geologist, you would think perhaps he would have been curious about that.
  • "Invaders from the fifth dimension!", was a statement later made in the episode of Star Trek: Voyager, Bride of Chaotica!, by a 1930s style robot.

Production Timeline Edit

Links and referencesEdit



Special guest starEdit

Uncredited co-stars (alphabetical)Edit


alien; book; chess; dimension; eye; Luminary's species; necklace; rock; scanner; shovel; wristwatch