Gus and Shawn end up as guests at a strange and secret party on Psych. "100 Clues" is the 20th episode of the show's sixth season.
Added:

Psych Season 7 Episode 5 Quotes

Lassiter: As of 2100 hours we are on a phase 4 lockdown!
Billy: Phase 4? What happened to the other three phases you cheap bastard?!

Lassiter: You know what happens in prison when you cry Harvard? A bunch of inmates go to the library and check out a bunch of books you've probably read before and beat you until you forget you ever went to...care to guess?
Martin: Harvard...
Lassiter: You really are smart.