Seth.

Carter's father, Jacob, enlists the SG-1 team in his hunt for the ancient Goa'uld Lord Seth, whom he believes is hiding on Earth. A computer search reveals Seth has maintained power on Earth for thousands of years using false religion, and the SG-1 team trace him to a heavily armed compound in Washington state.

Outside the compound they clash with a team of ATF men led by the adversarial Hamner, and a frantic father who is desperate to rescue his son Tom from Seth's cult. O'Neill, Carter and Daniel break into the compound but within minutes they fall victim to the biological agent Seth uses to brainwash his followers into doing his bidding.