Counselor Troi becomes pregnant by an alien energy-being; it develops from embryo into a human child in a few hours. The Enterprise transports a deadly plague virus to a research lab.

Patrick Stewart (Capt. Jean-Luc Picard)
Jonathan Frakes (Cmdr. William Riker)
LeVar Burton (Lt. Geordi La Forge)
Michael Dorn (Lieutenant Worf)
Marina Sirtis (Counselor [Lt. Cmdr.] Deanna Troi)
Brent Spiner (Lt. Commander Data)
Wil Wheaton ([Acting Ensign] Wesley Crusher)

Whoopi Goldberg (Guinan)

Diana Muldaur (Dr. Katherine Pulaski)
Seymour Cassel (Lt. Cmdr. Hester Dealt)

R.J. Williams (Ian Andrew Troi)
Colm Meaney (Transporter Chief [O'Brien])
Dawn Arnemann (Miss Gladstone)
Zachary Benjamin (Young Ian Andrew Troi)
Dore Keller (Crewman)

• Ian Troi is named after Deanna's father.
  
• Several crew changes are made beginning in Season 2: Geordi is promoted to full Lieutenant (from junior grade) and made Chief Engineer. Worf is made permanent Chief of Security. Dr. Pulaski replaces Dr. Crusher as Chief Medical Officer; Dr. Crusher has transferred to head Starfleet Medical. Wesley decides to stay on board, and replaces Geordi as the conn officer.
  
• In physical appearances, Troi begins wearing her hair down, while Riker has grown a beard. Wesley has a new gray uniform and now wears a comm badge.
  
• Dr. Pulaski is transferred to the Enterprise via shuttle from the U.S.S. Repulse NCC-2544.
  
• Guinan, the bartender in the Ten Forward lounge, is introduced in this episode.
  
• Though she has replaced Gates McFadden, Diana Muldaur's casting credit appears as a "Special Guest Appearance" during the first act, not in the opening credits. According to Rick Berman (who was against the idea), some of the "powers that be" believed the Dr. Crusher character was not working and should be replaced by someone with a personality more like Dr. McCoy from the Original Series.
  
• Due to the Writer's Guild Strike, Season 2 started much later than normal and consisted of only 22 episodes.