Talk to Aventus Aretino

Walkthrough
This quest can begin a number of different ways:


 * Ask innkeepers about rumours.
 * Speak to the children at the Honorhall Orphanage in Riften.
 * Overhear conversations either between guards in Windhelm or in particular between Idesa Sadri and Grimvar Cruel-Sea.

Any of these situations leads to learning about boy who has been practising the Black Sacrament.

Talk to Aventus Aretino
The Dragonborn simply needs to enter the Aretino Residence in Windhelm and speak to the boy. Sprich mit Aventus Aretino