The second part of the quest Contract: Devil by the Well. Geralt first brews some Swallow potions and some Specter Oil, then burns the remains and the bracelet to force the Noonwraith to appear and fight him.
Devil by the Well is the first monster contract in the game and in it Geralt is tasked with getting rid of a Noonwraith haunting a local well. As the name suggests, Noonwraiths tend to appear when the sun is high in the sky, which is why the ghost isn’t there when I first visit in the morning.
Monster Contracts are side quests in The Witcher 3 that you can take on for extra money and experience. You usually get Monster Contracts from notice boards.