Play the knight errant and have the favour returned.
The Witcher 3: Rough Neighbourhood
This is a two-parter quest found in Oxenfurt - yes, Oxenfurt is considered part of the Novigrad map. Back in your box.
Start at the Oxenfurt Harbour signpost. Wander south and you ought to find three mercenaries hassling a woman. Approach them and no matter what you say they'll end up battling you. Try to leave your sword sheathed and take them out with your fists; if you do so you can chat with their target, one Dora, and escort her home.
If you return to Oxenfurt a few days later and you may be ambushed by five mercenaries in an alley. Dora leaps to your rescue. Defat the baddies together to complete the quest.