Divide and Conquer (S04E05)

During a meeting with the Tok'ra high council, Maj. Graham of Stargate Command goes berserk, firing uncontrollably upon the Tok'ra before taking his own life. SG-1 is stunned to discover that Graham was a Zatarc, the victim of Goa'uld mind-control technology. According to Anise, its victims are subconsciously programmed to kill, their recollection of the procedure covered by false memories. Anyone who has come into contact with the Goa'uld could well be a Zatarc — and wholly unaware of the fact. Through the use of an experimental testing device designed by the Tok'ra, Anise sets out to determine who at Stargate Command might have been programmed. The test proves successful in uncovering a second Zatarc — Lt. Astor, a former teammate of Graham's, who also goes berserk, shooting up Stargate Command before turning her weapon on herself. Subsequent testing then uncovers false memories in two more members of the Stargate program: Col. Jack O'Neill and Maj. Samantha Carter. (Metro-Goldwyn-Mayer (MGM))