SPOILERS:
They start with a "On previous episodes of South Park" stuff with Chef leaving. It then cuts to real-time with chef returning and everyone rejoicing. They soon notice that Chef is not himself. Trey and Matt spliced Chef lines from other episodes, making all of his lines "I want to make sweet love to children", etc. The kids find out that Chef was with Super Adventure Club and they brainwashed him into a child molester. They are able to break chef out of the brainwashing by taking him to a strip club. The SUper Adventure Club re-brainwashes him and as chef is returning to the mansion (crossing a bridge), the bridge collapses and he supposedly dies (the fall from the cliff along with getting mauled by animals). The Super Adventure club re-animates him as Darth Chef, but this is unknown to the people of South Park. At the funeral, (I can't remember whether it was Stan or Kyle), but they said, "A lot of us don't agree with the choices the Chef has made in the last few days. Some of us feel hurt and confused that he seemed to turn his back on us. But we can't let the events of the past few weeks take away the memories of how Chef made us smile. We shouldn't be mad at Chef for leaving us. We should be mad at that fruity little club for scrambling his brains."
Nice little shot at Scientology at the end.