The Dink Network

Let's see... When you first enter the town, you must find and rescue Dertin in the storehouse northwest of town. Then you must go to Dertin's house and talk to him. Then you must talk to Sahib in the guarded house, leave, and rescue the hunting party. Then you must go back to town, enter the Sahib's house, and get Alessa to join you. Then you must enter the Shaman's house and talk to him. Then you need to go to Dertin's house and talk to him. Tell him to go with you to fix the water problem. Jump in the well in the eastern part of the town... You'll be in the water caves.

EDIT : And by the way, Alessa will leave you when Dertin joins you.