During the night the Robinsons witness the arrival of an alien spacecraft. The Robot says two entities are aboard. In the morning, Don, John, Will and Dr. Smith go out to investigate and find the spacecraft. Don and John go inside to look around and it appears to be empty. However, as they are examining the contents of the ship, the door suddenly closes and they are trapped inside. Will and Smith wander away and meet a pirate with a metallic parrot perched on his shoulder. The pirate says his name is Alonzo P. Tucker and that he was the one who arrived on the spaceship. Tucker demands they tell him where he is, but Will says that they are lost and do not know.
Captain Tucker takes Will hostage and sends Dr. Smith back to the Jupiter 2 with his list of demands. The Robinsons are to fix his damaged ship and give him all their cigars and cheese. Tucker treats Will kindly and entertains the boy with tall tales of the pirate life. Will begins to idolize Tucker very quickly. Tucker even lets the boy take the pirate’s oath to make him part of his crew. Tucker promises that when his ship is repaired he will take Will pirating with him.
The next day, as Captain Tucker and Will walk to the Jupiter 2, they come across a strange alien machine that seems to be searching for something. Tucker assumes it is searching for him and smashes it with a rock. When Tucker arrives to negotiate with the Robinsons, they promise to give him all the assistance and parts he needs for his ship if Tucker releases his hostage. The Robinsons invite Tucker to dinner while his ship is being repaired and he tells everyone how he was abducted by aliens more then a century before.
While making repairs to Tucker’s ship, John and Don discover it is equipped with hyperdrive, which can transport the ship anywhere in mere seconds. They ask Tucker if he would return them to Earth, but he does not know if he wants to help them. Dr. Smith does not want to wait for Tucker to make up his mind and plans to steal the pirate ship for himself. While Will and Captain Tucker are talking about the hyperdrive an alien spaceship arrives and Tucker flees in terror. Will runs after him and asks what the matter is. Tucker is too frightened to explain, but says that an “awful thing” is after him.
The “awful thing” is a large, shapeless blob that seems to be immune to all weapons and is able to pass through the Jupiter 2's force field. The Robinsons are worried that the creature is invincible and will destroy them. They deduce that it is looking for something, and Tucker admits that he stole a device from the creature's planet. When Tucker drops the device outside, the creature retrieves it and leaves immediately. The next day, Captain Tucker decides that he must leave, but without any passengers. When Will reminds Tucker of his promise to take Will on as his crew, the captain reveals that it was all only a story—he was never a pirate, only a scoundrel. Will is devastated, but his parents appreciate Tucker's honesty.
- The series begins its transformation from action/adventure into camp with this episode.
- Dr. Smith identifies the year of this episode as 1998.
- This is one of four episodes where Alpha Control issue equipment is installed in alien spaceships, and works properly! The other three episodes are "Blast Off Into Space", "Mutiny in Space", and "Collision of the Planets".
- One of Tucker's last memories of Earth involves hearing the news of the Battle of the Little Bighorn, which took place in June, 1876. He was abducted by the aliens shortly thereafter.
- Tucker demands cheese and cigars from the Robinsons. And he gets them. Apparently the Jupiter 2 was equipped with an Alpha Control issue humidor!
- The gelatinous alien who chases after Tucker, to retrieve the prognosticator, resembles a modified version of the bubble creature from "The Derelict."
- Why did Captain Tucker print his name on his hammock? Is there a lot of hammock-theft going on in outer space that we should know about?
- Why does Will claim he has no idea what planet they’re on? Just two episodes ago in “Return From Outer Space” Will knew exactly where they were and even called the planet by name. Is he lying to Tucker, or did he just forget all that information?
- Why was Will carrying a safety pin around in the pocket of his pants?
- Tucker demands that the Robinsons give him the spare parts he needs to fix his broken ship. Since his ship is clearly alien, how can he be so certain that parts from an earth-made ship like the Jupiter 2 would be compatible? How could he be sure the Robinsons would even know how to repair alien technology at all? And how did the Robinsons find or manufacture parts suitable for the alien ship?
- Why does Captain Tucker walk like he’s got a constant wedgie?
- Albert Salmi would later appear in Dallas as Gilbert Therman
- Albert Salmi tragically killed his wife and then committed suicide in 1990. This makes Professor Robinson's warning that facing the blob would be "suicide" an "aneurysm moment" (See Tvtropes.com).
- In the cliff-hanger refresh, the Robot warns John and Don of an approaching alien vessel. As the mechanical man moves toward them, the tow cable pulling it can be seen dragging in the sand.
- When the alien blob creature from Signet 4 absorbs the Forecaster device, you can see several sets of footprints in the sand after the creature moves out of shot.
- John and Don are trapped aboard Tucker's spaceship for what seems like hours, and now it's night time. "Gee Don, it must be time for us to push some random buttons so we can get out" Hey presto! The hatch opens! Why did it take them so long to try this logical course of action?
- When it comes time for Tucker to leave at the end, why don't the Robinsons, Don, and Dr. Smith press him further about going back to earth. As John pointed out earlier, Tucker could make several trips to get them all back to earth if needed.
- Now that Tucker has a spaceship, why hasn't he returned to earth?