Crichton begins to experience hallucinations as a result of prolonged periods of space travel. Meanwhile, Chiana brings a creature called a Vorc on board. She hopes that the creature will find and destroy the parasites that are contaminating the food supply. While walking through the ship, Crichton sees a beast of some kind. The others think he is hallucinating until D'Argo is attacked by the creature and injected with venom. Now the crew has to get a sample of the beast's DNA.