This quest spans the entirety of the game and is activated automatically at the end of the Prologue. After the death of Leo the Witchers embark on a quest to find out more about the Salamandra and go in search of the Professor, a wanted criminal, and the Mage. This quest takes Geralt to the Outskirts of Vizima which is where we pick up this quest in Chapter 1.
In order not to provide any spoilers I haven’t provided all of the information for the quest for the entire game here. Instead you can see the next step for this quest in Witcher’s Secrets Chapter 1.