The episode begins at a look at the concept of loneliness. It shows the viewer that solitude is truly one of the worst forms of punishment for a person's crime. The actor does a fine job of displaying his utter frustration of his sentence until he is brought a companion in the form of a robot.
Long before there were films about AI that would make us question what the exact terms of "life" actually is, we see how the relationship with this man and his female robot develops into one of love and devotion, and how the robot is "killed" at the end when the man's sentence is complete. Just like the convicted man in the story, we begin to see this robot as real, and wonder if the qualities she exudes do not qualify her as human.
Just like in all "The Twilight Zone" episodes. this story leaves us with an ending that makes us think long after the closing credits have finished.