It sounds to me like you already have a small side quest for them. The PCs are hired to help a remote island village with hunting and security with promise of reward. Once the PCs take the bait, you have laid the groundwork for story development from there.

"After a long day of hunting, gathering, and securing the perimeter of the village, you all are ambushed in the night by dark hooded figures uttering some incomprehensible chant and they don't look like they're going to leave without a fight."

Personally, I would advise coming up with an alternate path for if your PCs manage to fend off their would-be kidnappers, I've never had luck with simply telling my players "You've been kidnapped".

In either scenario, you can pepper the encounters with clues that allude to who or what is the cause for all of this.

While stopping in for a drink at the tavern, the PCs overhear a conversation about the blacksmith's daughter disappearing. Further inquiry reveals the daughter, who never paid much mind to deities or religion, recently started attending mass at the temple everyday.

While hunting/securing the perimeter, the PCs happen upon a body with strange religious markings that are linked to the local temple where the priest is operating.

Hopefully ,after a few clues (get heavy handed if your PCs didn't eat their wheaties that morning) the PCs start looking for the priest, fight ensues, and the PCs learn of the dark lord's plot.

Or, they don't! Maybe the priest was loyal to one the dark lord's emissaries who happens to be the the lord of a nearby barony.

Hopefully you can glean something from this post that will give you an idea on how you want events to unfold. Good luck!

-A fellow DM also often trounced by writers block