Villagers are unusually happy
The PC's get the uneasy feeling that something is not right. That feeling of someone has stepped on their grave.
While the villagers are friendly every now and then the PC's catch a look in one of their eyes as if they want to warn them of something but change their mind. Not all of the villagers they meet but a few.
Everyone though seems to never look beyond to the island or tower that can be seen across water from the village and when the island is brought up the subject quickly changes.
At the Tavern its like most lively with music, drinking and the like. Seems normal but is it? Once the PC's are sitting at a table and have ordered either food or drink they will receive a note handed to them (not in plain sight) but secretly by the bar wench as she serves them. Question is do they read the note or dismiss it?
A wizened old ferryman is the only person willing to transport the PC's to Wizard's Isle, but for for an exuberant price, but conversely, offers the return trip for free... what terrible fate waits for the party at the tower that would make the ferryman lift his charge for a return trip?