When the Dead Arise

Louise has been missing for almost five years. Me and Jake go out to a forest near our sister's house and a letter falls from a tree. It reads as follows:
Dear Alice, Jacob, Roxanne and Liliana Rose,
    I am delighted to say that Louise is still alive and safe. Come to this spot tonight. All of you. If you girls give me your utter devotion and loyalty, Louise’s life will be spared. If not, well, I’d rather not say what would happen to this innocent young lady. This is your only chance.
                                                       Sincerely,
                                        The Overlord
Now, we must find Louise and save her from the Overlord. But is this the end? Or has it only just begun?