Find Velwyn at the The Count's Arms and give him 5000 septims to buy the manor. He will then give the Hero the manor deed and the key to the front door. When they first sleep in the manor, they will be visited by three Benirus Manor Ghosts. so it's advised to bring a silver or a better weapon to kill them easier.
After dealing with the ghosts there is a crash downstairs, head to the first floor and on the floor is a broken vase, a piece of paper entitled Scrap from Lorgren's Diary. and a Skeletal Hand all surrounded by a green Glow. Both of these items are necessary for the quest later.
Reading the paper reveals the house is cursed and haunted. They'll need to talk to Velwyn again, but he has left Anvil. Don't forget to bring along the piece of diary when meeting up with Velywn as he will not offer to come back with them otherwise.
Talk to people in The Count's Arms and the Hero will learn that he went to the Imperial City. Head to Imperial City and ask around for Velwyn and people will say that he's staying at The King and Queen Tavern in the Elven Gardens District.
Talk to Velwyn again and he'll say that his grandfather was a necromancer who mysteriously disappeared when the Mages Guild was fed up with his necromancy. and ended his life.
He will then agree to go back to Anvil to help lift the curse, but his disposition with the Hero must be at least 60 or he will simply say, "Sorry, but how is that my problem?".
Velwyn opens the secret door
Return to Anvil, meet Velwyn at The Count's Arms. and follow him to Benirus Manor. Once inside, there are more Benirus Manor Ghosts. The Hero can ignore them and head downstairs into the basement. Follow Velwyn to the Sealed Portal and he will open it, but afterwards he will run away, leaving the Hero there. This causes all of the ghosts to disappear, but only happens if the portal is opened.
Once inside, the Hero must activate Lorgren's Altar to proceed. Lorgren will speak and says he wishes to make peace with the Nine. In order to do so, the Hero must bring back his hand and activate his skeleton.
Lorgren Benirus has risen
Lorgren will then say how easy it was to trick the Hero and will arise from the dead as a Lich. Kill him and the curse will be lifted and the house will be restored. The hero can pick up both Lorgren's staff and the book Tome of Unlife to sell or keep.
Return to Velwyn at The Count's Arms for completion of the quest.