You'll likely come across this while doing Wine Wars: Vermentino. At the hidden treasure marker southwest of Prophet Lebioda Statue, you'll find several rotfiends around a dead body. Loot the body for a journal and key, making sure to read the journal, then head to Vermentino Vineyard.
In the search area, look around the base of the sunflowers to find the hidden chest and loot it to complete the quest.
- While tending to the problems at Matilda Vermentino's vineyard, Geralt happened on a curious note.
- It suggested one Augustin Tonneliay had not been an honest man. Somewhere within the confines of the vineyard, he had stashed a considerable sum - his proceeds from illicit sales.
- Geralt found the treasure chest and emptied it of its valuable store. The now-dead, dishonest Augustine simply no longer needed it.
- Read Augustin Tonnelliay's journal.
- Find the chest hidden in the sunflower field.