
Should you lie to Niellen?
The "Wild at Heart" quest in The Witcher 3: Wild Hunt presents a difficult dilemma. While searching for the Blackbough hunter's wife, you will learn that it wasn't wolves that got her… It's never that simple, is it? Now you have to decide whether to tell a lie, investigate further, and perhaps even choose between two monsters.
Here's how to reach every "Wild at Heart" quest ending in The Witcher 3: Wild Hunt.
[Ed. note: This guide contains spoilers for The Witcher 3: Wild Hunt, so continue at your own risk!]
"Wild at Heart" is a secondary quest located in The Witcher 3's Velen region. The recommended character level is level 7, but you're free to start this side quest as soon as the game's prologue is finished — in other words, on your first visit to Velen. To start "Wild at Heart," collect the "Missing Wife" notice from a notice board.
Once you've read the notice, speak with Niellen, the hunter who posted the contract. You'll find him in Blackbough, in front of his hut.

Optionally, talk to the butcher and the butcher's wife, then head into the forest to look for Hanna, where a pack of wolves will attack you. After you've defeated the wolves, Margrit, Hanna's sister, will intercept you and demand you lie to Niellen about what happened to Hanna.
The first choice in "Wild at Heart" is to accept Margrit's bribe, or refuse.

Accepting Margrit's proposal is the only way to lie to Niellen. If you insist on finding Hanna, you're locked into the quest endings where Niellen dies (more on that below). Furthermore, if you accept Margrit's proposal, there's a point of no return for the "lie to Niellen" option: Once you've seen the werewolf, you can no longer spare Niellen. In other words, if you took Margrit's money, you can freely investigate Hanna's death, find the Isolated Shack, and still fast travel to Blackbough to lie to Niellen, as long as you don't enter the shack's hidden cellar.
To continue the investigation, whether you agreed to stop looking for Hanna or not, use your Witcher senses in the same glade where you fought the wolves. On the southwest edge of the glade, you will find Hanna's corpse. From there, follow the trail of claw marks, torn clothes, and werewolf scent until you arrive at the Isolated Shack northwest of Blackbough.

You'll find an interesting note on the floor inside the shack, but to find the real clue, the werewolf's lair, walk behind the shack. Down the slope, underneath the shack's main floor, you'll find a door to a secret cellar. As mentioned above, entering the cellar fails the "lie to Niellen" quest objective (if you initially agreed with Margrit).
If you wish to uncover the truth, blast the cellar's door with Aard (telekinetic blast) and fight the werewolf. Once he's got only a sliver of HP left, Margrit will interfere, asking Geralt to spare the werewolf (who turns out to be Niellen). You have two options:
Taking both key choices into account, there are three possible quest outcomes for The Witcher 3: Wild Hunt's "Wild at Heart" quest. To learn what has become of the survivors (if there are any), return to Blackbough after a while, where the peasant sitting behind the northeast house will be glad to share the latest gossip.

Including the direct impact of each choice as well as the peasant's information, here's a list of all endings along with their long-term consequences:
The best outcome for "Wild at Heart" remains up for debate, but if you don't mind a werewolf roaming the countryside, sparing Niellen seems the kindest option. You will also receive the most money if you choose this path: 55 crowns from Margrit and 10 crowns from Niellen.