Unlike many other games, The Witcher 3 offers a lot of dilemmas. More than once, Geralt has to decide the best course of action, and his decisions can either save or end lives. "Wild at Heart" is one of the side quests with multiple possible endings. Geralt can find the notice for it on multiple notice boards including those in Midcopse, Mulbrydale, Crow's Perch, and Inn at the Crossroads.
The contract's issuer, a hunter named Niellen, resides in Blackbough. Niellen is looking for his wife, Hanna, who mysteriously disappeared. When Geralt decides to take on the contract, he has no idea it will be more complicated than he thought.
7 Talking To Niellen And Margrit
When Geralt arrives to Blackbough, he finds Niellen standing in front of his hut. He refuses to go inside because he keeps looking for Hanna. Hanna's sister and Niellen's sister-in-law Margrit made soup for him but Niellen refuses to go inside and eat it. Geralt approaches Niellen and talks to him about the contract. If Geralt asks Niellen about Hanna's behavior prior to her disappearance, he learns she was happy and it's unlikely she left her husband and went to a different village.
6 Interrogating Witnesses
If Geralt agrees to help Niellen and look for Hanna, Niellen and Margrit will suggest two people Geralt can talk to. The first of them is the butcher's wife, Glenna, Hanna's friend. Glenna has no useful information for Geralt. She confirms Niellen's words, says that Hanna was happy and had no worries.
Second, Geralt talks to the local blacksmith and his children whom Hanna used to watch. One of the children, a boy reveals he saw Hanna going to the forest with another lady the morning she disappeared. However, he's not able to describe the other woman.
5 Going Into The Forest
At this point, Geralt knows that the best course of action is to follow in Hanna's footsteps. He goes to the forest and finds a pack of wolves. Once he kills them, Margrit appears. She says Geralt should look for Hanna no more as she's surely dead. According to Margrit, whoever disappears in the war-ravaged Velen doesn't return. Margrit wants Geralt to tell Niellen that he found Hanna dead and not to investigate any further. Geralt has the option to interrogate Margrit about her motives. If he decides to accept her offer, Margrit will pay him and leave. Geralt will get 80 crowns and 55 experience points.
From now on, there are two options. Geralt can either return to Niellen and lie to him, just like Margrit wanted. If he does, Niellen will offer to pay him. Geralt can either take the money or refuse. If he lies and accepts the reward, he gets 10 crowns and 50 experience points. If he lies but refuses the reward, he gets only 30 experience points. Either way, the quest ends there.
Another possibility is to accept Margrit's money but then continue investigating, regardless. When Geralt encounters Margrit later on, he says he changed his mind.
4 Continuing The Investigation
If Geralt decides to continue the investigation, he still has a lot of work to do. He should examine the dead dog the pack of wolves had previously surrounded. Geralt discovers bloody human remains nearby and deduces it's Hanna. Apparently, a werewolf tore her apart. By using his Witcher sense, Geralt also discovers claw marks. He should follow them to a stone leaning against a tree. Geralt makes a remark that he can't climb the tree. Instead, he should look for a tuft or fur nearby. That will allow Geralt to pick up the werewolf's scent and follow it.
The scent trail will lead Geralt to clothes on the ground. Geralt notices someone tore them off their body. A shack stands near. Geralt examines the shack and determines it's a hunter's shack. He finds some mysterious notes inside. The author of the notes confesses he's a werewolf. Judging by the notes, the werewolf who killed Hanna is none other than Niellen himself.
3 Fighting Niellen
Once Geralt leaves the shack, he should examine its closest surroundings. He'll find a trail of blood that will lead him to the werewolf's lair, a cave. If Geralt enters the cave during a day, he needs to wait or meditate until it's nightfall. Niellen will show up in his werewolf form and will attack Geralt. The fight is challenging since Niellen is fast and strong, but by using the Witcher signs and dodging, Geralt can do a lot of damage.
Once Geralt lowers Niellen's health bar enough, a cutscene will start. Margrit shows up and stops Geralt from killing Niellen. Margrit then reveals what really happened. She knew that Niellen was a werewolf and was in love with him for years. But he chose her sister. Margrit took Hanna to Niellen to make her see what Niellen was. She thought that Hanna would leave her husband, disgusted by the fact he's a werewolf. But Niellen tore Hanna apart instead without realizing it was his wife.
2 Two Possible Destinies
When Niellen realizes what Margrit has done, he threatens to kill her. Geralt has a time limit to choose one of two options. If he lets Niellen kill Margrit and walks away, Niellen will murder her. He will then catch up with Geralt and ask him to kill him. Geralt obliges and ends Niellen's life. If Geralt decides to protect Margrit, he'll have to fight and kill Niellen. Margrit will run away and Geralt will later find her crying at the abandoned shack. Either way, Geralt will get 50 experience points, and the quest will end.
1 Extra Details
The quest's suggested level is 7, but just like with any other quests, it doesn't hurt for Geralt to level up beforehand. If Geralt chooses to accept Margrit's offer and lies to Niellen, that's not the end of the story. If Geralt returns to Blackbough later, he learns from one of the villagers that both Niellen and Margrit died. In case Margrit survives, a random dialogue will reveal she left the village, possibly to look for happiness elsewhere.
When Geralt kills Niellen, he can loot a key from his body. The key unlocks a chest in the shack which contains some valuable loot.