Head to Carsten where, soon after entering the village, you'll see several men gathered outside a barred building and possibly hear some monstrous sounds from within.
Approach and talk to them and you can choose to just leave or suggest you can help them. If you respond to leave, one will recognize you as a witcher and say they need your help, going to the same options as if you said they could use your help directly. They'll then ask you to take care of the monsters within.
Important: after talking to them, the quest icon will soon disappear if you leave and a day has passed. If you return, you'll find that the monsters did break out and, while there are no bodies, the village is deserted.
If you agree to help them, they'll let you in but, to prevent whatever is inside from getting out, will bar you in until the monsters are dealt with. Inside you'll find 4 ghouls. Once you kill them off, the men will re-open the doors however, if you want to learn more, examine what the ghouls had been feasting on before you entered.
Once you've looked around, head back out and, if you examined the bodies, they'll tell you they were bandits. You can then tell them they should bury them or ask for your payment now. If you didn't examine the bodies though, they'll reward you all the same. Regardless if you looked around, they'll reward you with 25 and 20 , completing the quest.
- Near Novigrad Geralt came across a village whose inhabitants had themselves a bit of a ghoul problem. These nasty necrophages had taken up residence in their barn and posed a threat to the living. Geralt agreed to help the peasants - for commensurate pay, of course.
- Getting rid of the ghouls did not prove much of a problem for the witcher. A few chops and slices and he was ready to collect his reward.
- Kill the ghouls.
- Collect your reward.
- Despite this quest occurring around Novigrad, the quest log puts it as a Velen quest.