When his attempt to make rain during a drought destroys their weather station, Dr. Smith is banned from camp. After walking some time, he comes across an alien's spacecraft. He decides to use his discovery to force the Robinsons into taking him back, but when he finds that none will even speak to him, he takes a repair kit and begins to work on the ship alone.
The crashed ship is not actually a derelict, but a sort of space life boat that crashed on the planet. The ship’s owner, Admiral Zahrk, was cast adrift by his mutinous crew led by one Mr. Kidnoh; he hides himself and allows Smith to begin repairs, continuing them himself when Smith is not around.
When Will visits Smith at the crash site, he, the Robot and Dr. Smith are impressed by Admiral Zahrk as his crew. Zahrk plans to lift off in pursuit of his mutinous crew and retake his ship.
Will feels sorry for Doctor Smith and sneaks him some parts and some food. Zahrk grabs Will and takes him onboard the spacecraft, intending to blast off and chase after his long-time enemy, Mr. Kidnoh. Luckily for Will the spacecraft is still too damaged to fly, so he manages to escape and run back to his family. Will manages to escape, but after he returns to the damaged ship when his parents do not believe his story Zahrk recaptures him and they lift off.
John finds Zahrk’s log when he is searching for the missing Will. He begins work on a magnetic beam that will capture Zahrk’s craft and force it to return to the planet. Meanwhile, Will and the Robot are enjoying their new lives as sailors, but Smith’s ineptitude soon results in him being outranked by both Will and the Robot. When Smith is thrown in the brig for stealing cheese, Will and the Robot stage their own mutiny. This delays their journey long enough for John to lock onto the vessel and bring it back to ground.
Once the ship has landed, Will, the Robot and Smith disembark, but Admiral Zahrk blasts off immediately to continue his search from Mr. Kidnoh and the rest of his mutinous crew.
- "The best laid plans of mice and Smith" is a reference to the 1785 poem "To A Mouse On Turning Her Up in Her Nest With the Plough".
- During the scene where the Admiral is leaving the planet in his repaired spaceship with Will, Smith, and the Robot, he refers to a star being used for a navigational sighting as "Fornack". The robot refers to the same star as "Fontax".
- Doctor Smith pretends to repair the broken spacecraft so the Robinsons will pity him. Why doesn’t he really repair it and fly back to Earth like he’s always wanted to?
- Why is Zahrk’s ship so very tiny on the outside and so huge on the inside?
- When Zahrk suddenly appears, why aren’t Doctor Smith and the Robot more surprised to see him? They don’t even ask who he is.
- The Robot asks Doctor Smith if he wants to bet, and Smith refuses, stating that betting is vulgar. However, in the episode “The Curse of Cousin Smith” Doctor Smith spend a great deal of time playing with a gambling machine.
- Why did the Robot’s computers “get very dry?” Why did they get better again seconds later?