Surgery

Walkthrough
After loading the Dawnguard DLC, now and again the Dragonborn will hear from either City Guards or innkeepers:


 * "People say there is someone in Riften that can... change your face. Make you look completely different. Do you believe that?"

Once this happens, the quest is begun.

Locate the face sculptor in Riften
Once in Riften, the Dragonborn will overhear a guard disparaging the "face sculptor" and mentioning where to find her.

Talk to the face sculptor in the Ragged Flagon
Knowing that the face sculptor is at The Ragged Flagon, the Dragonborn can then decide to make use of her services.