03E14 - Foothold

After a vain search for the Harsesis boy on an unexplored planet, SG-1 is told there is a chemical leak and gets sedating injections in the infirmary. In fact star-base has been taken over by body-snatching aliens, as Teal'c and Sam discover, who are immune because of his symbiont and her Jolinar-remnants. Teal'c is captured while giving Sam the chance to escape; she meets with Colonel Harry Maybourne, who alas believes and brought the alien-possessed Jack and Daniel, who claim it's paranoia caused by the leaked chemical; during a flight back, Sam is able to see trough the game because of a 'flicker' and discovers it's done by two electronic devices to assume a human shape and voice. Meanwhile the real Jack and Major Paul Davis awake in an organic web where every human is tied into tentacles, soon meeting up with Sam and liberating Teal'c, in a hurry to try Sam's sound-idea before Maybourne sends in troops with orders to shoot and kill...