It was anchored by the fact that Will finally discovered Terri's fake pregnancy. He simply found her padded stomach and confronted her about it. A seriously emotional, anger-filled scene followed. Terri tried to plead her case, but Will left in a huff.
He ended up at school, where he actually managed to disqualify himself from sectionals. Here's why:
Earlier in the episode, Rachel has convinced the school's yearbook photographer to cast her and the club in a local commercial for a mattress store. It went very well, as the singers danced and sung to their version of "Jump." The mattress store owner rewarded the group by sending them a bunch of mattress... which Will found unopened when he arrived at school.. and which Will illegallly opened in order to sleep on.
But this was all a violation of the rules. Sue called the team out for destroying its amateur status, a fact Principal Figgins could not argue with. Will, though, took the fall because the team could have sent the mattresses back if he hadn't opened one. As a result, he took himself out of sectionals, but gave a passionate speech to the group:
If they can't succeed without him, he's failed at his job. Go get that trophy, New Directions!
Source: TV Fanatic