

Take down the Drowners and use your Witcher Senses to find a corpse that holds a key. There's also an alternate way in if you head outside of the city to the Glory Gate and locate the sewer entrance. If you didn't you'll have to pay 50 crowns or have Axii level two so you don't have to pay anything.

If you got the passphrase earlier you can get in without much hassle. Head to the next waypoint on your map and explain that you're a freak.

You can also ask any number of beggars in the area for additional information. Wait for a crime to be committed, then follow the thief to ask them for information. Head into the townhouse and loot the place using your Witcher Senses to find everything of value. Continue on to Triss' last known whereabouts and ask the looters if they know where she might be. Head into the Glory Lane district of Novigrad to find Hierarch Square where two people are being burned at the stake.
