Twovix Ensign Boimler learns that he is due to be promoted, while the Cerritos is escorting the decommissioned starship Voyager to Earth to become a museum displaying exhibits about its chaotic adventures in the Delta Quadrant. When a dormant Delta Quadrant "macrovirus" is awakened, Boimler's distraction allows it to combine with Borg technology, contaminate the other exhibits, and take control of the ship. After encouraging words from Ensign Mariner, Boimler enlists Ensign Rutherford's aid to disable the ship's systems with a sample of homemade cheese that once infected Voyager. Meanwhile, back on the Cerritos, a stray Delta Quadrant flower petal causes a transporter accident that merges Dr. T'Ana and chief engineer Billups into a single person, "T'illups". Captain Freeman learns that when this happened on Voyager, Captain Janeway killed the merged person, Tuvix, to bring back the original two individuals. Not wanting to suffer the same fate, T'illups begins "Tuvixing" other members of the Cerritos crew. Ensigns Tendi and T'Lyn end up merging all the Tuvixed individuals into a huge ball of flesh before separating them all out again. Once the chaos is over, Boimler, Tendi, T'Lyn, and Mariner all receive promotions to lieutenant (junior grade).