The Crystalline Entity returns, and a grieving scientist seeks revenge.
The Crystalline Entity strikes a new colony on Melona IV while the Enterprise is helping settlers there, and the crew shelters the colonists in caves before the creature strips the planet. Dr. Kila Marr, a xenologist who has studied the Entity for years, joins the hunt for it.
Marr's son was killed when the Entity destroyed the colony on Omicron Theta, Data's birthplace, and she is at first hostile toward Data because of his connection to Lore. As they work together, Data offers her logs and memories he holds from her son, and the two develop a way to contact the creature. Instead of communicating, Marr secretly turns the signal into a weapon and destroys the Entity, losing her career in the process.