Mercedes (Amber Riley), Santana (Naya Rivera) and Brittany (Heather Morris) have left the New Directions to join Shelby Corcoran's (Idina Menzel) all-girl glee club. When the two groups at McKinley High decide to "Mash Off," the girls perform a mash-up of Adele's hit songs "Rumor Has It" and "Someone Like You."
Here's how Fox describes the upcoming episode: "Sue (Jane Lynch) starts a smear campaign to take down her biggest competitor for the Congressional seat. Meanwhile, Puck (Mark Salling) has a crush, and Will (Matthew Morrison) and Shelby Corcoran (Menzel) encourage some friendly competition."
For a full list of the 300 "Glee" performances, click here.
"Glee" airs Tuesday nights on Fox at 8 PM ET.
To watch the performance of "Rumor Has It"/"Someone Like You," look below: