"The Key" was the eighteenth episode of Stargate Infinity.
When the team learns that a comet is headed straight for a planet they're visiting on which all communication is electronic, they also learn that the way to save this world is to decipher an obscure ancient text.
The team arrives on a civilized high-tech planet, Rokari, where they determine a comet is heading for the world they're on with only 60 hours to spare. The local government, the Commonality, don't believe their warning and state they have outgrown written and recorded language. The team break out a member of an underground resistance that distributes writing and leads them to a hidden library with info on how to use the planet's defense system. Harrison manages to figure out the language and the team activates the defense system, the Commonality sees the value of writing and everything turns out well.
Stacey: You should give me a sign when you don't mean what you're saying.
Gus: Don't you know me well enough by now?
Stacey: Apparently not.