The man who warned you about the ambush is telling you about his adoptive daughter who has vanished and who he suspects to be in the local crime lord's mansion. He asks you to break in there and look for her.
A swashbuckling mission inside the mansion. Just like stated in the mission description, the mission entrance actually is an upstairs window on the balcony at the front of the house.
Once inside, your opponents will all be level 22. You'll have to find the entrance to the girl's room (a separate instance) and enter it. You should be able to get there without meeting any of the guards. You'll find it's empty and will then have to leave the house again - this time, you'll use the front door. On the way there, you'll have to fight a group of guards. Leave the house and return to claim your reward.
- Get to the Girl's Room