You’ll find a corpse surrounded by a pack of Wolves. Make your way to the location in the woods and use your Witcher senses to investigate. The blacksmith’s children also have some information about the day Hanna disappeared.
One is the butcher’s wife and the other is the blacksmith. Use the quest markers to find the relevent people to speak to. The two of them will give you some details about Niellen’s missing wife including a few people to speak to and a location to investigate. He’ll be in front of one of the huts speaking with his sister, Margrit. Make your way to Blackbough and speak to Niellen.
Wild at Heart is a secondary quest that can be picked up by reading the notice boards at either Inn at the Crossroads, Midcopse, Mulbrydale or Crow’s Perch.