[Witcher 3] How to save Vigi the Loon

If you save Vigi the Loon, he'll participate in important events later in the game. It's not a difficult task, not even hard to figure it out, but it's kind of tricky that the game asks you to be sneaky only in certain moments and it's not a gameplay possibility during the entire experience. Would be really nice stalking some bandits while hiding in the field. The game could even force you to consider the wind direction while hunting beasts. That'd add more deepness into the gameplay.