Data (and inadvertently Lore) is called back by his creator, Dr. Soong, by a homing device in his circuits that causes him to take control of the Enterprise, while a young passenger is dangerously ill and in need of treatment at a nearby Starbase.

Brent Spiner (Dr. Noonien Soong)
Brent Spiner (Lore)
Colm Meaney (Lt. Miles O'Brien)
Cory Danziger (Jake Potts)
Adam Ryen (Willie Potts)
James Lashly (Ensign Kopf)

• Dr. Soong calls Data back to give him a chip that contains memories and emotion subroutines. Lore fatally injures Dr. Soong and steals the emotion chip.
  
• This is the first time Data meets his "father" face to face. It was previously thought that Dr. Soong was killed by the Crystalline Entity (see "Silicon Avatar").
  
• Data gets the emotion chip back in the 7th season opener "Descent, Part II", and finally installs it in Star Trek Generations. In the meantime, the chip's appearance would change from the tiny round disc seen here to resemble a large "Chex" cereal look.
  
• Lore was floating in space for 2 years until he was found by a group of Pakleds. He was found wearing a Pakled outfit. (See "Datalore" and "Samaritan Snare".)