Warehouse of Woe is a side quest in Novigrad. The suggested level is 13 and you will recieve 20 XP and 60 Crowns upon completion.

The quest is located by the Novigrad Docks fast travel point. Just follow the main road to the northeast and curl into the back of the biggest building. Once there you will see an argument outside of the warehouse.

Apparently a monster has gotten into a Dwarf's warehouse and he claims it was a racist human who put it in there, while the human claims he didn't do it. The guard hires Geralt to kill the monster and figure out who put the monster in there.

Once you've enter the warehouse you will encounter a lonely level 13 Nekker. Quickly kill the Nekker and use your witcher sense to investigate a dwarf footprint and a sawed of cage at the back of the warehouse.

Then head outside and tell the guard. They're two choices you can accuse the dwarf, who is most likely the culprit, or you can accuse the racist human. The choice is yours.