When SG-1 visited Vagon Brei, they found that all the inhabitants had died long ago. Many of the skeletal remains were found in their beds as if they had died in their sleep, and the planet had no signs of living birds or wildlife. Village records made mention of a mysterious sleeping sickness that many of the villagers believed was the work of Morgan Le Fay, who had cursed them for revealing her whereabouts when King Arthur and his knights came looking for her. Medical personnel from the SGC joined SG-1, but soon every member of the group began experiencing the overwhelming need to sleep.
Dr. Ackerman was the first to fall ill. His bloodwork showed an elevated white cell count and a marked increase in serotonin levels. His brain was also producing a surprising amount of melatonin, the hormone synthesized from serotonin that acts as a sleep-inducing agent. He had entered stage four sleep, also called Delta sleep or Slow Wave sleep and was unable to be awakened, but unlike the symptoms of a coma, he still responded to outside stimuli such as pain, sound, or touch. As all the members of the team began to exhibit early symptoms, they were unable to return to Earth, fearing that the illness was contagious, and they began taking heavy doses of amphetamines in an attempt to prevent them from slipping into the coma-like state.
In a soil sample taken from the nearby cave, Carter and Dr. Reimer discovered a dormant microscopic parasite that became active when in contact with live tissue. The parasite would enter the bloodstream and lodge itself in the brain where it would feed on melatonin until the compromised cranial tissue ruptured in a lethal aneurysm. On a planet devoid of animal life, Mitchell and Teal'c discovered a lizard-like creature in the cave. Believing it to have a natural immunity, Teal'c managed to capture the creature just as hazmat teams arrived to bring the team members back to Earth. Ackerman and Reimer had died on the planet, but using a sample from the lizard in conjunction with Dr. Reimer's research, Dr. Lam's team was able to synthesize a serum that starved the parasite and cured the illness. The members of SG-1 were able to make a full recovery.
Cross Reference: Bernard Ackerman, Dr. Grimsby, Hazmat, Dr. Reimer, Vagon Brei, Vagon Brei Lizard, Vagon Brei Parasite
Episode Reference: Morpheus