The elderly Lord of a small adventuring town was found missing from his home a after a visit from some strange men. The man's family determines that he has been kidnapped and hires the PC's to find him.
The PC's, following various clues, find the man, and, after a bit of a fight with Kenku and (some other bird race) the Kenku call for a truce. They say they were hired to kidnapped the man and the person who hired them has not shown up with their money. They want no more trouble with the PC's and hand over the old man.
So far, so good. What the PC's don't know is that the 'man' they take back is actually the Kenku leader, shape-changed into the old lord's appearance. The Kenku were able to use magic (my version allow them to be up to 3rd level mages) to ESP and CHARM the lord into telling them about his home, servants and treasure.
All goes well until a few days after the PC's return the 'lord'. It seems that most of the servants have been fired, guard captains dismissed for failing in their duties, etc. In other words, the 'lord' is clearing the castle of any who could recognize a difference in him. His family (if any - in my campaign there was a granddaughter set off to a nunnery and a son who was locked in the dungeon for treason - he was blamed for the kidnapping!!) have been done away with and most of the loyal servants/guards are gone. The 'lord' has hired new 'people'; more Kenku coming in as advisors, guards, etc.
Once this was done, they began cleaning out the castle treasury. Needless to say, the PC's will be curious, and the townsfolk furious. The 'lord' has diverted all monies to his "new and worthwhile projects" while neglecting the town and allowing things to decay. In the meantime, servants (Kenku) are looking for a ship (with a captain that would not ask questions) to come to the castle's dock during the night. This does not go unnoticed by the PC's.
It all comes down to the Kenku, loading the castle treasure into the ship, and in the midst of this, the PC's come in and battle the Kenku and their mercenaries. They may also find the true lord and his son in the castle dungeon.