Warning to all Gleeks: you are about to come down with a serious fever. A Saturday Night Fever, that is!

Actually, a Saturday Night Glee-ver, as is the title of this week's new episode, which will take viewers back to the 1977 film that made a star out of John Travolta.

Storyline-wise, we presume Rachel and Finn will continue to deal with what's becoming a shaky future. Song-wise, meanwhile, we'll be treated to disco classics from a past era, including covers of Mercedes-led version of "Disco Inferno" and a Blaine-anchored rendition of "You Should Be Dancing."

Watch the full performance of each now:

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.