"The Breeder" is the nineteenth episode of the third season for the science fiction television show Sliders. Upon arriving in a world where 18-25 year olds are mandatory organ donors, Quinn, Rembrandt, and Wade have to see about removing a parasite from Maggie's body.

Five minutes before the slide, Quinn, Maggie, Rembrandt, and Wade are running through a tropical bog fighting off amoeba-like parasites that are trying to attach themselves to them. Just before they slide, Maggie is hit in the face by one. When she is cryogenically frozen in the next world and taken to a hospital, it's discovered that the parasite deposited a larva into her that is controlling her motor and body functions. Maggie escapes, but the others soon catch up to her. Just then a van rounds the corner and two members of the Donor Squad (also known as the "D Squad") pick up Quinn and Wade and place implants in their wrists.

All 18 to 25-year-olds in this United States are required to have these implants and are picked off the street whenever someone needs an organ transplant. Rembrandt escapes this requirement due to his age, and while he's planning to rescue Quinn and Wade, the larva in Maggie's body takes control of her and tries at first to implant her (or its; Quinn surmises that the parasite creature is an hermaphrodite) eggs into Rembrandt. She escapes the hotel room and goes to a bar, then a condominium's heated pool, and then a spa to find both a male she can implant with her eggs as well as a constant heat source for the larvae to thrive in.

Quinn and Rembrandt find Maggie back at their hotel room; Wade was taken captive by Dr. Sylvius for the forced organ donor program when she threatened to reveal that Sylvius wanted to harvest the creature in Maggie's body to learn how the creature replicates so quickly, thereby allowing organs to be grown rapidly and eliminating the need for the mandatory donor program. Unfortunately, the way Sylvius plans to extract the creature would kill Maggie. Dr. Sylvius volunteered to release Wade if she was allowed access to the symbiotic creature inside Maggie. Quinn and Rembrandt freeze Maggie's body and return to the hospital, and Quinn enters the freeze room to coax the parasite out of Maggie's body. He reaches for the creature with tongs, but it's too strong for him to hold. Wade, Rembrandt, and Sylvius rush in to help him, but the creature escapes and crawls into Dr. Sylvius' open mouth as the others, Quinn, and Maggie slide. After the vortex closes, the symbiont -- now in control of Dr. Sylvius -- begins to evaluate potential breeders.