During a not-fully-planned-and-thought-out adventure to the Everfree Forest to earn their Cutie Marks, the CMC are used as tools to spread a monstrous plague throughout all of Equestria… unless they can control themselves for the good of their species. And learn how to use their powers in the first place.

Note: Told from varying first person views. I'll tell you which pony in the Author's Note, so pay attention.

[spoiler]This is a Vampire Story! :)[/spoiler]