Doctor Kila Marr was a Human xenologist and former resident of the Omicron Theta colony. She had one son, Raymond, born in 2320. Prior to 2336, Dr. Marr left the colony to pursue her career and left her son, nicknamed "Renny," in the care of the Wallace family, friends who remained on the colony. Although she kept in contact, Marr never found the time to return to the colony before Renny was killed in an attack by the Crystalline Entity in 2336. Dr. Marr experienced a great amount of guilt over the fact that she did not make it a priority to visit her son, and channeled her feelings into studying the Entity and examining its attack sites.
By 2368, Marr was renowned as the foremost expert on the Entity. She studied at least three different attack sites, including one at Forlat III, and also developed a method to modify photon torpedoes in order to destroy the Entity. That year, she visited the USS Enterprise-D following an attack on Melona IV. Marr was excited, as this was the first opportunity to examine a site so soon after an attack. She also wanted to interview the survivors as no one had ever escaped the Entity before. She was suspicious of Lieutenant Commander Data, who was on Melona IV during the attack, and believed that the Entity spared the colonists because of his presence. Furthermore, she thought Data was in collusion with the Entity just as his brother, Lore, had been responsible for leading the Entity to Omicron Theta.
Eventually, Marr began to warm to Data after Captain Picard forced her to work with him in order to develop a way to track the Entity. Together, they discovered that the creature left residual antiprotons as it moved through space.
The Enterprise-D set course to pursue the Entity after it was located and Marr wanted to make preparations to destroy it once it was found. Captain Picard objected, feeling it would be better to try to communicate with the Entity and attempt to reason with it before resorting to violence. Marr vehemently disagreed with this plan, as she felt that the Entity was no more than a "killing machine" and was beyond redemption.
She reluctantly agreed to work with Data again, this time to develop a way to use graviton pulses as a means of communication. By this time, Marr had apologized to Data and realized that she was presumptuous in accusing him of leading the Entity to the Melona colony. She also learned that Data contained some of Renny's memories, experiences, and journal entries (which had been programmed into Data as an attempt to allow him to better interact with Humans) and used Data's knowledge to learn more about Renny, most importantly that he did not blame her for leaving him on the colony.
Shortly following, the Enterprise-D responded to a distress call from the freighter Kallisko, which was attacked by the Entity and had all organic matter on board, including its crew, absorbed. The incident with the Kallisko made Marr think further about Renny and wonder about his final moments. Eventually, she had Data tell her more about Renny and even read one of his journal entries in his voice. The entry was especially poignant as it took the form of a letter to Dr. Marr, where Renny discussed a recent test and said that he missed her a great deal.
The Enterprise-D eventually caught up to the Crystalline Entity and began emitting graviton pulses in an attempt to communicate. The pulses worked, and the Entity began responding with a series of its own pulses. However, Marr, blinded by vengeance and remorse over Renny's death, initiated a continuous graviton beam and then locked out the controls. The beam caused the Entity to vibrate rapidly and eventually shatter, destroying it.
The Enterprise-D bridge crew were aghast and Picard ordered Marr confined to her quarters. Data escorted her there, and Marr again wanted Data to take on the voice of Renny. She specifically wanted him to tell her that he understood why Marr had destroyed the Entity, and that he was now at peace. However, Data was unable to comply with her request. His knowledge of Renny made it clear that he had always been proud of his mother's life as a scientist, and that he would have been disappointed and upset that his mother had ruined her career. Marr was left to contemplate the consequences of her actions. (TNG: "Silicon Avatar")