Tasha Yar's sister appears on the world where Tasha was raised.
The Enterprise travels to Turkana IV, the lawless world where Tasha Yar was born, to rescue the crew of a crashed freighter held by one of the planet's warring factions. A member of the rival faction offers to help, and she turns out to be Ishara Yar, Tasha's younger sister.
Ishara helps with the rescue plan, and Data, who had been close to Tasha, forms a friendship with her. The crew begins to hope she might leave Turkana IV and even join Starfleet.
During the rescue Ishara breaks away to sabotage the rival faction's defences, revealing that she had been using the Enterprise for her own side's ends. Data stops her, the hostages are freed, and Ishara is returned to the planet. Data reflects on the betrayal and on his memories of Tasha.