The quest may be started by speaking to a crying courtesan just outside the front entrance to Crippled Kate's brothel. It turns out that Skelliger warriors have occupied the brothel to drink and revel, while declaring it "territory of Skellige". The courtesan and her friends are willing to pay to have you evict the warriors for them. When you enter the building a cutscene begins in which Geralt speaks to the lead warrior.
You have three options, but you can't use your weapons, potions, or any Signs during this quest.
1. Offer to fist-fight the level 15 leader one-on-one; if he loses all the warriors leave. This encounter is not too difficult, just counterattack once to break his combo then keep pounding away until his stamina runs out. After that he stops blocking your attacks and it's an easy victory.
2. Threaten the group and fist fight all three of them (two level 1 warriors, and one level 15 warrior) at once. They can be a challenge to beat seeing as they're all rather large and the fight takes place in a cramped area. Ample dodging and blocking is recommended while keeping your back to the open room to escape for a small reprieve.
3. Use the Axii sign to convince them to leave and receive 40.
There is also a fourth option which is unlocked by completing The Lord of Undvik quest, which requires you to have already progressed some way through the main story in Skellige. Picking this option allows Geralt to persuade the warriors to leave by way of his reputation.
Exit the building and speak to the courtesan again. She expresses her gratitude and offers a reward. You can accept the gold reward, or refuse it.