Beverly becomes romantically involved with a Trillian ambassador who is being escorted by the U.S.S. Enterprise to mediate a dispute in the Peliar system. As the starship approaches its destination, Riker volunteers to shuffle the ambassador, Odan, to Peliar to meet with representatives of the planet's Alpha and Beta moons, which have armed for war against each other. Shortly after Riker and Odan depart, a ship opens fire on them, critically injuring Odan and forcing their return to the U.S.S. Enterprise. Back on board, Beverly's examination of Odan indicates that a parasite is invading his body. As she prepares to remove it, she is shocked when Odan stops her, revealing that he is the parasite, and his body is merely a host. The parasite, not the body, is what must be saved.
