While you are out adventuring, you will stumble upon a dog named Barbas. He will communicate with you and explain the situation. Barbas is having problems with his master, and needs your help. Follow Barbas, he will take you to the Shrine of Clavicus Vile.
The Shrine of Clavicus Vile is located inside Haemar’s Shame Cavern. You don’t need a follower on this quest. However, get ready to fight vampires and other enemies. Bring enough health and cure disease potions to last you for a while. Barbas will act as your companion. He will also fight alongside of you.