Although the Borg do not appear in this episode, nor are they mentioned by name, they are responsible for the destruction of planets near the Romulan/Federation border in the season one episode "The Neutral Zone". They make their first official appearance in the season two episode "Q Who" and subsequently appear in "The Best of Both Worlds" (1 & 2), "I Borg" and "Descent" (1 & 2). They are mentioned but not seen in "Family" and "Star Trek Generations". Their final Next Generation appearance is in the film "First Contact".