While investigating a massacre at Federation outpost Ohniaka III, the Enterprise encounters the Borg, whose individual identities and viciousness trigger a startling change in Data.

Brent Spiner (Lore)
John Neville (Sir Isaac Newton)
Jim Norton (Albert Einstein)
Natalija Nogulich (Vice Admiral Alynna Nechayev)
Brian J. Cousins (Crosis)
Professor Stephen Hawking (Himself)
Richard Gilbert-Hill (Bosus)
Stephen James Carver (Tayar)
Joyce Robinson (Ensign Gates)
Guy Vardaman (Lt. Darien Wallace)

• Physicist and Trek fan Stephen Hawking has a cameo, appearing in Data's poker game intro.
  
• Admiral Nechayev chews out Picard for not using Hugh to destroy the Borg in season 5's "I, Borg". Picard watches footage from that episode on his ready room viewscreen.
  
• Picard puts Crusher in command of the Enterprise while the bulk of the crew searches for Data and the Borg.
  
• Jim Norton also played the holodeck Einstein in the episode "The Nth Degree".
  
• This is the first appearance of Lore since season 4's "Brothers".
  
• Data experiences his first emotion, anger, followed by pleasure.
  
• The main title and credits usually occurs after the teaser, before Act One. However, in this episode, the teaser (the holodeck scene) moves directly into Act One (which starts on the bridge, along with the title text "Descent" followed by the credits). The main titles occur in the middle of Act One after the reveal of the Borg drone.