The series follows the adventures of the Federation starship Voyager during its journey home to Earth, having been stranded tens of thousands of light-years away. In this episode, Neelix and Paris have a personal falling out after which they are sent on an away mission together where they must reconcile their disagreements with each other to help keep a newly hatched alien infant alive.
Relations between Neelix and Lt. Tom Paris fall to a new low when they have a fight in the mess hall over Kes. Captain Janeway calls both of them to her ready room for an assignment. They show up covered in food, having spilled it on each other during the fight. Janeway is not amused and cautions both of them to put their differences aside. Voyager's food supplies are low, and they are being sent to a planet, nicknamed Planet Hell for it's hellish conditions, which they believe contains edible material, based on the proteins which show up in scans. Due to Neelix's role as chef, and Paris's position as the ship's most experienced pilot - there are atmospheric conditions which will make landing a shuttle difficult - they have been chosen to scout the planet. On their way to the planet their shuttle crashes due to the environmental interference.
The planet is coated in a poisonous trigemic vapor which forces Paris and Neelix to seek shelter. They find a cave and blast the rock to cover the entrance, assuming that they will be rescued before long. Once inside the cave, they discover a nest of eggs, and as they watch one of them hatches. Paris and Neelix debate what to do with it, with Paris wanting to leave it and Neelix believing that, as they have trapped it in the cave with them, they have a responsibility to care for it. Meanwhile, Voyager attempts to find the lost crew members are halted when they are attacked by an alien ship, which places itself between Voyager and the planet in an attempt to block access to the surface.
Paris and Neelix discuss their argument over Kes. Paris confesses that he is attracted to her, something which he has always denied, but that he respects her choice to be with Neelix. The two of them struggle to care for the creature, and before long it appears to be dying. It will not eat their rations, but they surmise that the vapor outside must be the source of the protein they saw in their scans, which are blocked by the stone they blasted in front of the entrance. Once they bring the creature outside and force-feed the vapours to it by means of a medicine dropper, the creature recovers. Paris and Neelix are overjoyed, though they quickly begin to exhibit symptoms from the trigemic poisons. Voyager disables the weapons aboard the enemy ship, and moves into the planet's atmosphere to rescue Neelix and Tom. They refuse to be transported off until they are sure that the creature will survive. They hide, and just before it is too late, an adult of the creature's species appears to collect the infant.
Back aboard Voyager, Kes, who is glad to see Neelix's return, observes that Paris and Neelix have formed a friendship based on respect.
"Parturition" was written with the speicifc goal of resolving Neelix and Paris's animosity, and dealing with Neelix's jealousy over Kes once and for all. Executive Producer Jeri Taylor stated "...we wanted to create the feeling of a family, not a lot of people with resentments. So we were looking for a way for Paris and Neelix to resolve their differences and this plot worked out very nicely."Jennifer Lien, who portrayed Kes, was similarly positive about the change in her relationship with Neelix after this episode. She stated "I think Kes and Neelix still need to explore some issues of trust. I think Neelix's jealousy is getting to be minimal because the character is learning. They've grown in this relationship. When it becomes too obsessive, it becomes scary, and I don't think that's what the character of Neelix is about." The infant creature which appears in this episode was a cable operated puppet. Ethan Phillips stated that "It took six guys to operate that (puppet). Six guys and two girls, they were an eight-man team. There were all kinds of wires and levers and prods. It was very complicated but it was very realistic."