Overview
Following the Thread is a secondary quest in The Witcher 3: Wild Hunt, following Lambert‘s hunt for the killers of his friend Aiden, a witcher of the Cat School. It moves from Novigrad and the Seven Cats Inn to Faroe in the Skellige Isles, so Destination: Skellige must be done to finish it. It fails if not completed before Uma is retrieved in Ugly Baby, and the conversation at the Seven Cats Inn locks out Flesh for Sale.
A monster in The Bits
The notice “Contract: Monster in the Bits” on Hierarch Square leads to a supervisor who says some “brave fool” is already on the case. Claw marks lead across the river into a building, where Lambert is fighting an ekimmara. When they go to collect the reward, Lambert attacks the supervisor, leaves Geralt to deal with the guards, and finishes the man off. Then he asks Geralt to meet him at the Seven Cats Inn.
Aiden’s killers
Lambert explains: an assassin named Jad Karadin and his gang murdered Aiden. One of them, Vienne, drinks at the inn. She says she does not know where Karadin is, but names two others, Selyse and Hammond. The talk can end peacefully, or in a fight with her and three elves. Lambert suggests they split up, and Geralt takes Hammond on Faroe. Crach an Craite can tell him more about Hammond beforehand.
Hammond
Pirates guard the entrance to Trottheim. Hammond himself is at a shrine at the eastern end of the island. After a few words he and his men attack. His body carries a letter from Jad Karadin. Since patch 4.01, Crach pays a reward for Hammond’s death.
Jad Karadin
Back at The Nowhere Inn, Lambert has learned that Karadin now lives in Novigrad as a wealthy merchant under another name. His guards take the two witchers straight to him, and he turns out to be a retired witcher himself. Karadin claims his band had to kill Aiden because Aiden turned on them. Geralt can spare him or help Lambert kill him. Lambert is angry if Geralt spares him, but there are no further consequences.