Shady merchant was an unnamed man located on the Velen side of the Border Post in 1272, where he made and sold counterfeit transit passes for refugees looking to cross over to Redania. Even though this was technically illegal, the nearby guards knew about this and even made hints to others that there were other ways to obtain a pass.
If Geralt talks to him: he'll offer Geralt a pass for 100 . If the witcher balked at it, he then offered a discount if the witcher would help his brother-in-law, Albin Hart.
If Geralt helps Albin and he survives: pleased, the merchant then offered to sell the pass to Geralt for 25 .
If Geralt helps Albin but he dies: upset over this, the merchant refused to do anymore business with Geralt.