Talk to Captain Bezique. He gives you Bezique's Letter.
Take the letter to Neti. She gives you Neti's Dagger and Bow. You can only use these two weapons during the entire quest, so take a lot of Soulshots - they're weak against Undead.
Go to the Ruins of Sorrow (Ruins of Agony). Hunt Spartoi (with the dagger or bow) anywhere in this area or to the northwest of the walled ruins until you collect 10 Spartoi's Bones. You can also hunt Skeletons, but they rarely drop the bones.
Give the bones to Neti and you get a Horsehshoe of Light.
Give the horseshoe to Bezique and he gives you a Wanted Bill.
Hunt Cat's Eye Bandits (with the dagger or bow) until you collect the 4 stolen items - Stolen Necklace, Stolen Tomes, Stolen Jewelry and Stolen Ring. They are along south side of the road from Gludin to Gludio. Take some friends to deal with all the other Ol Mahums (up to level 30+), or just be very careful to find the bandits alone.
Talk to Captain Bezique. He takes all the quest-related items and gives you Bezique's Recommendation.
When you are level 20, talk to Grand Master Ramos (Gludin) to become a Rogue.