Anvil Mages Guild
Go to Carahil in the Anvil Mages Guild. She'll request that you investigate a series of deaths on the Gold Road and wants you to help solve the problem there. She'll send you to see Arielle Jurard who is at the Brina Cross Inn.
 Brina Cross Inn
The Inn is just along the main road east from Anvil. It's very close to the city and won't take long to get to. Once there find Arielle and she'll insist you rent a room using a traveling merchant disguise. Speak to Christophe Marane and rent a room for the night. You may want to talk to Caminalda who is also in the inn to tell her that your a traveling merchant. Go to your room and wait for Arielle. Once she comes up talk to her then sleep in the bed for however long you like.
 The Gold Road
The following morning head east on the main road and meet up with Arielle and a battlemage named Roliand Hanus. They'll follow you to find the murderer. Carry on a bit and you should run into Caminalda who turns out to be the culprit! Killing her with your two allies is not much trouble. Once she's dead head back to Anvil and collect your reward from Carahil.