After destroying a deadly asteroid in the Pelloris Field, the Enterprise heads toward the Moselina System unaware that a strange particle cloud has contaminated the ship.
En route, Lwaxana Troi (Majel Barrett) beams aboard and announces her plans to marry a man she has never met. Much to her daughter's dismay, she accompanies Worf's son Alexander (Brian Bonsall) to the Holodeck and introduces him to her hedonistic lifestyle.
Meanwhile, the crew finds that the mechanical parts around the ship are being mysteriously transformed into gelatinous material. When the life support systems begin to fail, the crew discovers an alien parasite from the asteroid is causing the problem. As they search for a solution, an even bigger disaster looms on the horizon: Lwaxana and her husband-to-be are completely incompatible!