First Season Episodes - Welcome Stranger (episode 6)

A long lost astronaut visits the Robinson's stranded spaceship and enlists their aid in returning his vessel to outer space.

Upon investigating a blip on the radar screen, John, Don and Will discover a spaceship piloted by Jimmy Hapgood, a spaceman who missed a landing on Saturn fifteen years earlier and has been in space ever since. Hapgood' s arrival sets off a train of thought in John's mind. He feels is not fair to keep Will and Penny in their dangerous surroundings. His wife, Maureen, agrees with his thinking. 

Smith eavesdrops on their conversation and becomes incensed as he has already considered Hapgood as his own transportation back to Earth. The Robinsons broach the subject of having Hapgood transport their children to Earth. The answer, Smith rejoices, is no. When Smith smugly approaches Hapgood later with the suggestion that he accompany the astronaut, the spaceman flatly tells Smith he does not take passengers. 

The next day, as he is about to take off, Hapgood discovers that a fungus has covered the spaceship as a result of a spot Will failed to decontaminate. Before Hapgood can stop her, Penny is seized by the grasping fungus, and she is engulfed as he struggles to free her. Will gets a tether line and loops it about Hapgood so that they can both use their strength to free Penny. 

His feelings about the children are altered considerably by this near-tragedy, and Hapgood speaks to the Robinsons, offering to take the children. They agree, and while they are making preparations to send them, Smith tries to talk Hapgood out of taking the children. He turns his efforts on Will and Penny, saying their parents do not wish them to leave. Word that their parents do not want them to go is enough for the children, and come blast-off time, they are nowhere to he found. Hapgood leaves on schedule - without Smith. 

Later, Don and John set out to blast a mine when Penny, unaware, runs into the blast area just as the switch has been set to fire.

Filming