While Riker, Crusher and Data survey Melona IV for colonization, the Crystalline Entity appears unexpectedly and attacks the planet, forcing everyone underground. Dr. Marr arrives on the Enterprise to help track the Entity and she accuses Data of bringing the entity, as his brother Lore once did.

Ellen Geer (Dr. Kira Marr)
Susan Diol (Carmen Davila)

• The Enterprise first encountered the Crystalline Entity in the first season episode "Datalore".
  
• Colony director Carmen Davila is killed in the attack when she tries to help an elderly colonist.
  
• Dr. Marr's 16-year-old son, Raymond "Renny" Marr, was killed on Omicron Theta when Lore lured the entity there. Dr. Marr feels guilt over leaving her teenage son with friends while she pursued her career.
  
• Data carries the journals and some memory fragments of the Omicron Theta colonists in his positronic net. As Dr. Marr becomes more unstable, she asks Data to read one of Renny's letters... in Renny's voice (which comes across as slightly creepy).
  
• Dr. Marr ultimately destroys the Crystalline Entity with graviton pulses.