Legacy (S03E04)

The SG-1 team discovers a room containing the corpses of a league of Goa'uld who challenged the system lords. One holds a tablet; after Dr. Daniel Jackson touches it, he begins to hear voices and see nightmarish visions. Medical tests indicate Daniel is suffering from schizophrenia. Whatever is interfering with his mind, however, soon transfers to Teal'c — with far more deadly consequences. As the Goa'uld parasite leaves Daniel's body, Daniel hears the voice of the dead Ma'chello declaring death to the Goa'uld. Daniel realizes that he was infected by Ma'chello's Goa'uld-killing parasite, a theory borne out by Teal'c's rapid deterioration. Believing the tablet holds the key to Teal'c's survival, the team brings it to the lab. As they open the tablet, though, the parasites ooze into medical officer Dr. Janet Fraiser, Maj. Samantha Carter and Col. Jack O'Neill. Carter proves immune, but with parasites inside them, Fraiser and O'Neill deteriorate rapidly. Gen. Hammond has no choice but to seal the lab off with the three inside. (Metro-Goldwyn-Mayer (MGM))