Settle a ghostly marital dispute.
The Witcher 3: Blood and Wine - Til Death Do You Part
This quest can be found on an NPC in the 'Clever Clogs' Tavern in Beauclair, which is just a short way from the cemetery. The NPC is upstairs, and is marked on the map with an exclamation point. It can also be found via a noticeboard. It's suitable for Level 36 and up.
Once the issue has been explained to you, head to the cemetery. There's lots of things you can investigate with your Witcher senses, but only one matters: find the large set of stairs more or less in the middle of the area and head down. Enter the catacombs and keep going down until you find some grave robbers.
Kill the grave robbers and be sure to loot the bodies, since a note on one unlocks the treausre hunt quest 'The Last Exploits of Selina's Gang'. Once they're dead, meditate until after 8pm. Head back up to the cemetery proper - you'll hear a noise. Head back down the catacombs below and into the small room on your left as you first enter.
You have to do a full Witcher-senses investigation of the area to progress, even though the investigation turns up nothing. Leave and now head back towards where you killed the bandits - but then a loud noise will draw you back to the room you just left. Hide behind the statue and hit the trigger to wait there... and all will be revealed.
So, the ghosts of a married couple are arguing. Here you're faced with a choice: remove the urn of the wife or the husband. Your rewards will differ depending on what you do. Here's the rub:
If you remove the wife's urn, you'll be directed to place it elsewhere and then when you return to the quest giver he'll thank you for stopping the ghosts with the a decent magical sword. The ghost of the husband offers you nothing.
If you remove the husband's urn you'll have to fight a few more grave robbers, but the wife will then give you directions to a place where you can then engage in a bit more combat and find the Barclay Els and Vampire: Bruxa Gwent cards. When you return to the quest giver he'll still reward you, but sadly only with coin rather than the sword.
Which of these characters you'd rather help and which reward you'd prefer is up to you - but once you turn the quest in, it's marked as complete.