The Vengeance Factor

After a Federation outpost is raided, the trail leads to the Gatherers, piratical nomads descended from Acamarians who broke away generations ago. Picard brings Sovereign Marouk of Acamar III aboard to offer them a way home, and Riker helps with the negotiations. Along the way he becomes attracted to Marouk's young servant, Yuta. When an elderly Gatherer dies suddenly, Dr Crusher finds a genetically engineered microorganism designed to attack one clan's DNA. Records show that Yuta was present at an identical killing decades earlier, yet she has barely aged. The truth emerges: Yuta is the last survivor of the Tralesta clan, wiped out by the Lornak clan 53 years ago, and she has been altered to hunt down every remaining Lornak. The Gatherer leader, Chorgan, is one of them. Riker beams down to stop her. When Yuta ignores his warnings, he fires at increasing settings until she is destroyed. Peace between the two sides then goes ahead.