First, talk to the guard by the fence. Enter the mansion and walk to the room in the east, where a dagger lies on the ground. Take the Silver dagger and the Murder Scene pot, then investigate the window to get a thread. Take note of the dog outside and search the gate for your second piece of evidence. Now; search the barrels found in most bedrooms. There are 2 barrels downstairs, and 4 barrels upstairs. If you've looked in each barrel, you should have these items:
Now, walk down the road to Camelot and find the Poison Salesman along the way. Ask whom he sold the poison to. He will tell you that everyone had bought some. Now, go back to the mansion and talk to the person whose fingerprints you matched. Ask them why they had to use his poison. Then, investigate the object they were talking about. A message will appear that there isn't poison in there. Go back and talk to the guard to receive your rewards.
Players who drop the thread will not be able to pick up the item again unless they cast Telekinetic grab on it. When players attempt to pick up the thread they receive the message Some <color> thread. Not enough to be worth taking.
Even if you have dropped the item. When you talk to the Sinclair children about the thread, your character will still somehow show the thread to them.