The Sword, Famine and Perfidy - The Witcher 3

In a certain cellar located near a nest of drowners, Geralt found a body. Quite curiously, the deceased had not been torn apart by the monsters, but seemed to have died of thirst, having been barricaded in the cellar by some third party. Near the body Geralt found a key and some notes, all of which he took with him.

Geralt had found his fair share of hidden treasure before, so he found the chest without too much difficulty and took its contents for himself.

From the notes Geralt learned about a treasure hidden in a locked chest on a ship. He suspected the key to that chest was the very one he had found by the body.