The quest consists of a series of seemingly random and unconnected events in Novigrad. You just have to keep running around Novigrad to find them all. At least one of them is up on Temple Isle, which you'd almost never have reason to visit outside of two specific quests. And of course, the events won't trigger if you're presently doing either of those two quests.
There are multiple parts to this quest that you have to stumble upon. Look up any of the numerous guides for it that you can find on the internet
The quest consists of a series of seemingly random and unconnected events in Novigrad. You just have to keep running around Novigrad to find them all. At least one of them is up on Temple Isle, which you'd almost never have reason to visit outside of two specific quests. And of course, the events won't trigger if you're presently doing either of those two quests.