Saving Evaine - NWN Side Quest (Chapter 2)
Saving Evaine is a side quest that takes place in Luskan and begins by speaking with Elynwyd in The Cutlass building. You can find The Cutlass in the southern portion of Luskan, it's marked on the map with its own note so you can't miss it. The town of Luskan is only available to you during the final part of Chapter 2.
For this quest Elynwyd asks you to rescue his sister Evaine from Kurth's Lair. During you conversation with Elynwyd make sure to get Elynwyd's Signet Ring from him as we'll need it for this quest. You'll have to successfully Persuade Elynwyd to get it which is annoying but do-able.
Evaine is found in the room adjacent to the one with High Captain Kurth. You can find Kurth in the north-central room of the Kurth's Lair map. If you need help locating either of these people use my screenshot below and look at where I am on the map. Talk to Evaine when you find her and she'll see Elynwyd's Signet Ring then thank you and run off.
To complete this quest and obtain your reward you'll want to return to Elynwyd in the Cutlass and speak with him.