Stargate is visited by general Jacob Carter on a mission -actually requested by his symbiont Selmak, who wants him to deal with his long-repressed break-up with Sam's brother Mark- to ask SG-1's help in the hunt for the sole system-lord the Tok'Ra never tracked down, Seth, the Egyptian god of chaos and total evil, who plausibly never left earth but hides as Ra put a high price on his head.