Where does Simon go after he leaves "the lord of the flies" and why do Ralph and Piggy decide to attend Jack's feast?

After Simon leaves his secret place where the hunters have put the pig's head, he staggers down to the beach.  Unfortunately for him, the boys are in a complete frenzy, doing their hunting dance.  Even Ralph has joined them.  This is because he is a bit afraid of the storm that is blowing up.  Jack says that they need to dance to prevent the storm from hurting them.

When Simon gets down to the beach, the boys end up treating him as the pig.  They beat him to death.  They do this because they think he is the beast.