This quest can be unlocked by meeting Peter Saar Gwynleve, garrison commander in Nilfgaardian Camp. It is done during the main quest Lilac and Gooseberries. In this new mission you must kill a giant griffin harassing the White Orchard. Before you fight the beast, you must prepare yourself - meet a hunter and a local herbalist. Both these meetings can be done in any order you want.
Hunter Mislav is living south from White Orchard Village. After reaching his house, knock to the door to see if he is home. Activate Witcher Senses and follow the footprints to the forest. Soon you will reach the place where hunter is hiding. Now you can either force him to tell you where the corpse was found or first help him with defeating wild dogs (350 experience points). The latter won't be hard. No matter how you acted, Mislav will lead Geralt to the place where he previously found body. Stay there for some time and thoroughly examine the territory (use Witcher Senses). Examine the empty alcohol bottle, blood tracks on the ground and footprints which you must start following.
Keep walking, you will get through a Broken Bridge. Climb on the higher ledge slightly further and jump towards the path further away. Soon you will reach the griffin's nest. You must examine it thoroughly. Check the corpse, bones and dead female griffin. Pick all the behavior options from the list shown on the screen. By doing so, you will learn about the dead creature (and receive some experience points).