I'm on the quest called "The Source" and this seems like the moment where you decide which romance path you want to take. I checked out both and have saved games when I chose Shani and when I chose Triss at the end of the quest. Just for the fact that I'm completely canceling out the other character. Shani is very nice and I'd probably like her more as a person but it feels right to be with Triss. I know it sounds like I'm making too big of a deal out of this but I'd rather the game play out in a way I'd like.
At the beginning of Chapter III, Triss gives Geralt three magic sensors and asks him to place them in some reliefs located around town. They will be used to triangulate the source of some strange magical anomalies she has recently noticed. Being the obliging soul that he is, he agrees to help her and heads out to find the reliefs in the Temple Quarter , cemetery , and Trade Quarter and place the spheres in each one. The witcher then must find Triss to let her know that the task has been accomplished. Actually, he does not really have to say much as she already knows.
This is one of the most beautiful quests in the game. When Triss finds imbalance in city's natural magic field, she tries to pinpoint its source. Geralt helps her by placing 3 sensors around the city. As it turns out, it's Alvin - he's Hen Ichaer, the Elder Blood, and his magic is so strong that it throws all the city out of balance.