A Bizarre occurrence causes Neelix and Tuvok, who are attempting to transport back to the U.S.S. Voyager from an away mission, to arrive aboard the ship as one. The crew is astonished when a strange but oddly familiar alien humanoid with dark speckled skin and pointy ears - which is neither Tuvok nor Neelix - appears. The Doctor's bio-scanner shows that Neelix and Tuvok's patterns have merged, causing the pair to become one entity - Tuvix. While Tuvix assimilates and starts to become a valued member of the team, Kes struggles with the fact the Neelix may not be a part of her life anymore. Meanwhile, the Doctor devises a method to restore Tuvok and Neelix, except for one variable - Tuvix does not want to die. When the Doctor, who is programmed to follow certain ethical guidelines, cannot perform the separation, Janeway is left with a monumental decision.
