This page of the guide to The Witcher Monster Slayer contains a detailed description of the third quest in the game - Good Money.
Rewards: 1200 XP, 40 gold coins.
You need to take the figurine to Margit. She will appraise it, give you gold coins, then smash the item against the ground. She'll find a mysterious note among the fragments.
She will ask you to find an endrega fetus in early development.
The nest will be marked on the map. You have to go to there and fight the monsters.
When you open the cocoon you will find that Dehael was inside, and he crushed everything inside the cocoon.
The next approach should go quite smoothly. Obtain the fetuses and go back to the researcher.
She will pay you for the quest and then won't be interested in you any longer.