Head to the house where, before you can enter, the new owner, Rudolf de Jonkheer, will greet you. You can ask him more about the house but ultimately he'll let you go in seeing as you're a witcher and might help with whatever is haunting the house.
Upon entering you'll hear laughter and the sound of footsteps and, as you start to head upstairs, you'll hear Corinne in distress. Head up and you'll see a godling, Sarah, standing over the sleeping oneiromancer. After a short cutscene, it's clear Corinne is under a sleeping spell and won't wake up normally. However, she does gives you 2 clues: the doll and the attic. With that, head up to the attic (the door opposite the bed) and climb up the ladder. Use Aard on the blocked doorway, then enter to find the rag doll and the drawing of a crib here. If you already explored the house, Geralt will comment he knows where the cradle is, but regardless, just head back down to the room Corinne is in and, in the only other room off of the bedroom, you'll find the cradle.
After you place the doll here, the door will close, with a drawing on the back of it. After interacting with it, go find the oven, which is all the way down in the cellar (the trapdoor is on the first floor right next to the stairs). Note that while there's a weakened wall here, you don't need to go past it for this quest. Interacting with the oven will cause another cutscene, this time formally meeting Sarah, who'll reveal she was just having fun and sees the place as her home and was just trying to get the banker to leave. You can answer however you like in the first part, but in the second choice, you have to decide to either make a deal with her (allowing her to stay) or force her to leave.
Let Sarah Stay
If you wish to let the godling stay, agree to make a deal with her, and she'll let the dreamer wake up so you can talk to her. Doing this will eventually see Rudolf sell the house to some "poor fool" and will give access to the secondary quest, Haunted House.
If you wish to make the godling leave, you'll need burdock. If you haven't already bought it, head to the herbalist across the canal (you can talk to Rudolf as you head off to get it, but the conversation doesn't yield much). When ready, place the herb on the oven, stand back, then use Igni. Sarah will throw some insults at you but relents and leaves.
Talk to Corinne
Regardless how you dealt with Sarah, head back upstairs to Corinne. After talking with her, she'll agree to help you and asks that you meet her at her room at the Golden Sturgeon. With that, leave the house only for Rudolf to stop you to ask about the haunting, as Corinne didn't tell him what happened. No matter how you dealt with Sarah and if you tell the banker the truth or not, Rudolf will ultimately decide to sell the house and asks that you visit in a week or so as he'll give you a percentage of the commission when he sells the place.
Enter the Golden Sturgeon and head upstairs to talk with Corinne. She'll ask that you answer some questions truthfully to better help you. While there are a lot of options to give, you only need to answer one, the rest will just give background on the relationship between Geralt and Ciri. She'll then ask about Ciri's abilities, and you can again answer however you wish, before Corinne finally asks who you think Ciri would have gone to. Either choice will then go to a cutscene showing Dandelion, a swallow, and an explosion. Afterwards, Corinne will mention that the bard had inherited a brothel, The Rosemary and Thyme. The quest will then conclude for 100 .
- Oneiromancers - or dreamers, as they are more commonly called - possess the ability their name implies to divine the future or relive the past through dreams. Corinne was one of the best of her kind and had no trouble finding clients, even with the hostility to the occult that reigned in Novigrad at the time. Geralt hoped she would spare him a few moments, and set off to find her in a house where she had gone to ply her trade.
- Corinne agreed to help Geralt and put together a dreaming séance for him. Geralt has always been an introvert and talking about his feelings and loved ones does not come easy for him. Yet that was exactly what the dreamer needed him to do if she was to dream about Ciri. In the end, Geralt forced open his shell, then fell asleep - and dreamed. In his dream, he saw Ciri in Novigrad... with me.
- Find the dreamer in the old house.
- Search the attic.
- Take the doll.
- Examine the drawing.
- Put the doll in the crib.
- Find out why the door slammed shut.
- Examine the oven.
- Make Sarah leave:
- Get some burdock.
- Burn burdock in the oven.
- Talk to the dreamer.
- Meet Corinne at the Golden Sturgeon.
- The name of the quest is possibly a parody of the song "California Dreaming" by the Mamas and the Papas.
- In the Polish (Original) version this quest is called "Sen w wielkim mieście" which is a play on "Seks w wielkim mieście" which is the Polish title for the TV series "Sex and the City". When translated literally it would mean "dream in the big city".