Simon Turner worked for the CIA in its earliest days during the Cold War and was a fervently outspoken opponent of the Soviet Union, especially because he believed no one could get rich in their socioeonomic system.
In 1947, archaeologist Indiana Jones was held at gunpoint by a Soviet soldier while investigating the Soviet dig site for the Infernal Machine in Babylon when Turner suddenly appeared and shot the soldier dead, saving Jones from capture. Turner showed further support for his fellow American by giving Jones the key to a nearby door; however, by instinct, Jones never fully trusted Turner.
Turner also convinced Jones to find for him a golden statuette of Marduk, claiming to want it as a passionate "art collector."
When Jones found out the first destination of his journey in search of the Infernal Machine's four missing parts, Turner tried to dissuade him, but Jones went off on his adventure anyway, later succeeding in collecting the pieces.
Turner and Jones crossed paths again in Anglo-Egyptian Sudan while in the presence of Sophia Hapgood, an ex-lover of Jones and Turner's subordinate in the CIA chain-of-command. Soviet Dr. Gennadi Volodnikov also appeared and demanded that Jones give him all the now-gathered Machine parts, since only he knew how to properly handle them. Forced to make a decision, Jones decided to trust his fellow Americans, relinquishing the pieces to Turner and Hapgood, who immediately headed back to Babylon to assemble them.
Hapgood, Turner, and Jones reunited in Babylon. There, Hapgood was beginning to question Turner's true motives, suspecting that he was being led by his own extremist ideology against the Soviet Union and might therefore recklessly use the Machine's power for personal gain. Turner thus worried about Hapgood's loyalty and Jones's defensiveness over her, and so shoved her into the cage that acted as the Machine's portal into an alternate reality called the Aetherium. He then grabbed hold of Taklit's part of the Machine, which had the power to make its user invisible. Jones confronted Turner, who believed his actions were justified in order to use the Machine to secure an American victory over the Soviet Union. After refusing Jones's demands to release Hapgood from the aethereal cage, Turner activated Taklit's part, becoming invisible. Unfortunately, Turner had installed the Machine parts in the wrong sockets, thus forcing Jones to go about reinstalling them in their proper locations.
While reinstalling the parts thus, Jones again encountered Turner in another room of the Infernal Machine, where Turner, still proclaiming his zealous views, attempted to outmaneuver and incapacitate Jones using his newfound invisibility powers and a pistol. Turner taunted Jones, yelling insults and discharging his weapon, while going in and out of invisibility. Jones drew his own pistol and, after a brief firefight between the two, shot Turner through the heart, killing him instantly.