Blue Eyes

Patrick de Weyze will give you this quest during chapter 3. You need to locate her missing sister, Blue-Eyes - she has been bitten by a vampire and ran away from home. Talk to Carmen for an update, then go to the House of the Queen of the Night in Vizima Trade Quarter and talk with Blue-Eyes. Make love to her, then ask her about the neck wound. She won't tell you much.

To be continued...