Received from: Notice board, the Nekker contract (M7, 5)
Step 1: Learn more about the Nekkers
The mission is very easy, but rather time-consuming. It's a good idea to take the contract from the board and continue completing other quests - the first part of this mission will pretty much complete itself. In order to learn more on the Nekkers' life, you just have to kill them. You can start doing it at the woods, where you will find lots of monsters. For example, you can complete Malena, during which you will visit a cave full of Nekkers.
Step 2: Use Grapeshot bombs to destroy the entrances to Nekker tunnels
Once you slay enough monsters, a proper information will appear and the second part of the mission will begin. Based on your observations, you will conclude that Nekkers use underground tunnels as means of fast travel. You have to destroy all four Nekker tunnels (M8, 4) spread throughout the woods with the bombs. You can find their locations on the map. Grapeshot bombs can be bought from Cedric (M7, 7), but considering their high price, it's better to buy the formula and prepare them yourself. You can find the ingredients both in the woods as at the local merchants.
Step 3: Collect you reward from Louis Marse
After killing both Queens, go to Louis Marse (M7, 15) from whom you can collect your prize. His apartment is to the left of one of the main gates.
Prize: 75 XP. Formula: Witcher's Superb Silver Sword.