Burlap is the New Stripe
Localised from this IGN wiki https://www.ign.com/wikis/the-witcher-3
This page contains IGN's Walkthrough for Burlap Is the New Stripe, the twelfth main quest of The Witcher 3's first DLC expansion, Blood and Wine.
Dark Days
Looks like Anna has thrown you into jail. After talking to another prison mate, you'll have control of Geralt.
Walk downstairs and use your Witcher Senses to find soap near the stairs and the dirty clothes opposite of the wash tubs. Grab both and place them in the tub. Grab the nearby stick and start giving them a whirl.
Remember the guys you beat up back in Where Children Toil, Toys Waste Away? They're back and ready for a rematch. Luckily for you, these guys are an even bigger pushover than before, so this should only take a few seconds.
A week will pass and a guard will summon you out of your cell. Follow him around the prison until he finally takes you to Damien. Still upset of recent events, Damien will begrudgingly release you as Dandelion has shown up and convinced Anna to let you go.
Aftermath
From here you'll meet up with Regis and have the option to pursue who the final victim was supposed to be, or skip straight to Regis and Geralt drinking at the cemetery.
Make your way over to the bootblack boy and question him further about the notes he received earlier on in the game. From there, follow the marker on your map to make your way to the beggar's shelter.
Get through some dialogue and cutscenes and you'll be thrown into a fist fight. At this point in the game, you so much as sneeze and these two thugs will be down. Chatter some more, and you'll eventually learn that Anna was to be Syanna's final victim. You now have the option to go and tell Anna about the truth. Otherwise, head to Regis to end the mission.
Run over to the cemetery where Anna is grieving. After telling her the truth and seeing a conflicted and grieving Anna, the duchess will harshly send you on your way, leaving you to go to Regis at the other cemetery. This will lead to the Be It Ever So Humble quest.