All evidence points to the fact that the attack on the town of Sandpoint is part of a larger plan and the ourlaws that are behind that plan are headquarters in Thistletop.
The PCs journey to the known goblin den only to find that goblins are the least of the problems they are going to face. Bring your own 3rd level characters or use characters that are provided. No evil characters please. You do not have to attend the previous sessions to attend this event. They are intended as a sampling of what the adventure path is like.