Even if it is not necessary to successfully complete it, or leave it uncompleted (the quest will automatically fail at the end of the Chapter), it is connected with a primary quest, Royal Blood.
This quest is a sub-quest of Royal Blood.
It can be triggered after the initial confrontation with the lynch mob in front of Stennis' room by asking three dwarves at the end of the hall about their suspicions. One of them (Zevro Hayek) mentions that the goblet that poisoned Saskia may have been crafted by Thorak. You don't get much more from him. The map will then indicate Thorak's whereabouts (his forge is next to Cecil Burdon's house).
If Thorak is still alive he will simply deny having made the goblet, leaving Geralt none the wiser about who poisoned Saskia.
This quest remains in the journal until Baltimore's Nightmare has been completed.
- There is limited time to question all the possible persons of interest during the Royal Blood quest (or at least the game gives that impression), so it is entirely possible to miss talking to some people. If you do not actually question Thorak about the chalice in particular, it is still easy enough to find his key and Olcan's receipt, but the quest is marked as failed in the journal.
- If you want to Support the Prince (fair trial) and complete The Walls Have Ears, do not complete Baltimore's Nightmare quest, talking to Cecil Burdon. Stop at the point when you have to either kill or spare Thorak. Then, in Royal Blood, when the riots arise, start questioning for opinions talking only to the peasants and the dwarf. Ask him about possible duplicate goblets. The dwarf will point you out to another runic master smith, Thorak, activating Suspect: Thorak quest. When the journal quest says "Wait for events to unfold", complete Baltimore's Nightmare quest, talking with the alderman. Now you can complete both Suspect: Thorak and The Walls Have Ears opening Thorak's locker in his house.
- Here the few steps to complete these four quests are listed, as already described above:
- After the riot breaks out (Royal Blood quest), talk to only the dwarves and peasants.
- Leave the riot and proceed to complete The Walls Have Ears until it reads "Wait for events to unfold."
- Proceed to complete Suspect: Thorak until it reads "Wait for events to unfold."
- Proceed to complete Baltimore's Nightmare until you kill Thorak.
- Finish Suspect: Thorak. Opening Thorak's chest should complete both quests.
- Walk to Cecil's home and finish Baltimore's Nightmare.
- Return to the riot and complete the scene based on the evidence you have gathered.
This procedure will allow you to complete both sub-quests and maximize experience as well as reveal the maximum amount of evidence. However, since you can only talk to two parties, this means you will be unable to hex the guards to Stennis's room and converse with him. If you would like to see what Stennis has to say (or any other non-essential party), make a save before talking to anyone at the riot, talk to Stennis (or other non-essential people), then reload the game. He does not provide any hard evidence to prove his guilt or innocence.
However, this quest and The Walls Have Ears will change from completed to failed after the quest Vergen Besieged starts.
- After talking to the creator of the goblet – which had been a gift from the fold of Vergen to Saskia – Geralt decided to visit Thorak. He suspected that the original goblet had been replaced with another, containing the poison. Thorak was the only artisan in Vergen capable of replicating the original and thus producing the goblet used to poison the Dragonslayer.
- Thorak insisted he had in no way contributed to making the replica. The criticism he leveled at the gift goblet could have indicated a genuine aversion, for one is never as honest as when in the grip of envy. Geralt had no idea what to do next, so he decided to drop this part of the investigation and focus on questioning the onlookers in front of Stennis' house.
- If, dear reader, you have not lost your way in the tangled but interesting tale of Geralt's stay in Vergen, you may remember Thorak, a dwarf who died by the witcher's hand. Geralt searched his corpse and found a key. And where there's a key, there's a chest. As it turned out, the contents of Thorak's chest was of import to the investigation of Saskia's poisoning.
- In Thorak's chest, Geralt found a note confirming receipt of an ornate item. Another man might have ignored the scribbles, but during his life our hero had read so many abandoned letters, notes and secret documents, that he could easily have become an archivist. Effortlessly, he recognized that the receipt had been penned by Olcan, and the item in question was a replica of Saskia's goblet used to commit the crime.