Last Rites is a Side Quest in Velen.

Travel to the bridge north of Blackbough. Note: she will only appear during the night.

She will say that her dead husband is haunting her and she wants you to put her ring near his grave, in order to comfort him in the afterlife. She would do it herself, but she is too scared to travel alone in the forest. So travel to the marker in the cemetery and use your witcher senses to find the grave. Once at the grave put the ring on it, then pull out your magic lamp to see two ghosts talking.

Travel back to the granddaughter Lessy's house in the village to claim your reward. There you will find out that not everything was what it seemed.