In the next new episode of Glee, we have Rachel's crush on Mr. Schue to look forward to...and the trigger - their duet together of Endless Love. By the look in Will's eyes, I'm guessing he's more than a little freaked out by this, and we learn the reason for that too. Take a look at these sneak peeks from Watch with Kristin for episode 10, "Ballad".
Source: E! Online