Scenes From a Marriage - Hearts of Stone
This quest automatically begins after you complete both Open Sesame! as well as Dead Man's Party. Both of these quests are Hearts of Stone Story Quests and they involve fulfilling Olgierd's three wishes, this quest involves Olgierd's third and final wish.
For the first part of this quest head over to the von Everc manor where you'll find a thief who is currently having a bit of a problem. Speak with him and then head into the estate's courtyard. There will be a few quest circles in here for you to examine, when you're done go to the front door and examine the lamp then follow the drag marks. When you are ready for a fight go into the back garden of the estate.
In the estate's back garden you'll encounter the Caretaker (pictured above) who will be your first boss fight of this quest. The Caretaker is most vulnerable when he does a wide swing and gets his weapon stuck in the ground; watch for this moment to strike and deal the most damage you can to him. When he gets low on health he'll start to summon spectral ghosts that walk towards him. You can kill them in one hit, but if the caretaker attacks them it heals him.
The Caretaker Weaknesses: Relict Oil, Quen
Once you've defeated the Caretaker head into the building and make your way to the living room where you'll find Iris' Sketchbook (pictured above). There will be a short scene in this room as well involving a wraith peeking out of a painting. Continue upstairs and there will be a lot of supernatural stuff along the way.
Upstairs you'll need to go outside and follow the balcony to the bedroom, on the otherside of the bedroom is a hallway where the next boss fight will take place. In here you'll be battling the wraith that we saw earlier. Prepare your weapon with Oil and your bombs/potions before going into this room.
Wraith Weaknesses: Specter Oil, Yrden (Also: Moon Dust seems to work here too)
For the majority of this fight the Wraith is going to be non stop in your face. Yrden will help you get a lot of hits in on her as will Moon Dust bombs. She has a few unique moves for you to watch out for but the main one is every once in awhile throughout the fight one of the paintings will "come alive" and begin to heal the wraith.
All it will take is one attack from Geralt to stop the painting from healing the wraith. Once you defeat the wraith head into the master bedroom on the other side of the hallway and loot the painting of Olgierd and his wife on the desk, grab any other loot you want from the area then examine the body on the bed.
When the scenes are all finished you'll be tasked with burying Iris' body. In the northern most portion of the estate's courtyard is where you'll find a suitable location, you'll have the option of placing her sketchbook or the painting on her grave too, I don't think either changes anything. There will be a scene with Iris leading Geralt into the world of paintings which is where you will be completing the next part of this quest.
In the world of paintings you'll have to visit multiple different memories of Olgierd and Iris which will give you some insight on how their marriage failed. You can do these memories in any order and in order to complete a memory you'll need to pick up objects in the surrounding area and place them in the right positions. Use your Witcher Senses to find the objects as they all glow red.
Iris and Olgierd at Gazebo: Put Book in Olgierd's hand and painting pallete on the table
Olgierd and Iris at Fountain: Put the Glass in Iris' hand
While you're in the world of paintings/world of memories you'll occasionally have to battle Specter spiders which have the same mechanics as the arachnomorph enemies. There are other threats for you to deal with here as well such as bees and even a boss later. Don't let your guard down.
Once you've completed the above two objectives head inside where you'll have to do the next part of the quest.
Dining Hall With Painting: Light the fire place and the two candles closest to the fire place, where everyone is sitting
Master Bedroom: Place the bloody towel into Olgierd's hands
After the master bedroom you'll come to the Painting Room which will have the most complicated puzzle yet (above). For this one you'll have to place the objects on the table in the same locations you see them in the picture above. Chalice is found to the left of the painting's easel and the bowl of fruits is found behind Iris.
Olgierd in Painting Room: Apple on the right, Chalice in middle and Grapes on the left
Master Study: Pick up the Chalk and Candles, place the candles on the circle surrounding the pentagram (Option #3)
After the brief cutscene in the study you'll need to escape the flames. Use the Painting on the wall to be teleported outside into the middle of a blizzard. To get back inside you'll need to find the cellar entrance which is to the west of the manor's entrance (as shown in my screen shot below).
Cellar: Place the mug in Olgierd's hand and the Marriage Contract in Iris' father's hand
Dining Hall (Final memory): Small Bowl in front of cat, Large Bowl in front of dog, Food Tray into Caretaker's hands
Once this scene is over continue into the next room where you'll have to inspect the letter on the table. If you need to meditate and heal up do so before inspecting this letter. You're going to be facing off against the final boss in this world of paintings/for this quest. The boss will be none other than the specter of Olgeird himself.
For this boss fight you'll have to fight all of Olgierd's phantoms - so long as you only attack one at a time you'll only have to fight one at a time. The moment you attack one of them it "awakens" and will begin attacking you. Parry works very well against these opponents as does Aard when they are using their most powerful attack. Moon Dust bombs and Specter Oil should be used too.
Note: If you awaken all of the opponents before defeating any of them then defeat them all at once you'll get the When it's Many Against One... Trophy/Achievement.
After the fight there will be some scenes and dialogue. During which you'll have the option of taking the Rose from Iris (which will free her) or leave her with the Rose which will leave her bound to this world as well as the two animals. If you choose to let her keep the Rose, you'll need to take the Rose from the Painting instead for Olgierd.
Freeing Iris and the two animals will net you a piece of advice from the animals in regards to O'Dimm, you should seek salvation in glass that cannot be broken. Once you leave the painted world this quest will complete and you'll receive the final quest in the Hearts of Stone Expansion, Whatsoever A Man Soweth.