To start this quest you need to talk to the Mysterious Merchant you can find in Novigrad. He will try to sell you some magical items he found in houses abandoned by mages.
When you agree to see the items he has to offer ("Show me what you got."), several witch hunters will appear nearby and the halfling will start running away. To receive this quest you cannot turn him over to the witch hunters, so you must choose the answer "Left his soup on the burner.".
Novigrad, the most cosmopolitan city of the North, attracts its fair share of oddballs and eccentrics. One of them was a merchant dealing in unusual goods. While talking to Geralt he spied some witch hunters approaching and fled at once. Still interested in the secretive merchant's secret wares, Geralt decided to hunt him down.
