Restless Ghost Quest
1. Teleport to Lumbridge and then go to the church there.
2. Speak to Father Aereck to begin the quest. He'll tell you that a ghost is haunting his graveyard and wants you to help him lay it to rest. He'll then ask you to speak to Father Urhney who is located in the Lumbridge Swamp.
3. Go to the Lumbridge Swamp (check minimap) until you find a house with Father Urhney inside of it. Talk to him about the ghost haunting Father Aereck's graveyard, and he will give you a Ghostspeak amulet that allows you to speak to the ghost.
4. Equip the Ghostspeak amulet and open the coffin in the graveyard. The ghost will appear, talk to him, and he says his head is missing from his body.
5. Go south until you reach the mining area. There will be a rock a little south of the fishing icon. Search the rocks and a Muddy Skull will appear in your inventory.
6. Go back to the Ghost, and use the Muddy Skull on the coffin.