Free will is a myth, as is most of the Christian faith.
The idea of free will is that God gave us the gift to make our own decisions. Of course accepting the gift of Jesus's sacrifice is supposed to be the ultimate use of this free will.
But free will cannot exist within the idea that all happens within God's plan. If God has planned out existence from the beginning through the end than free will has no effect. For everything to be planned, than all the decisions you make with your free will would have to be predetermined and therefore not really your choice.
For example, Bob has the option to either kill Chris or not. It is within the idea of free will that Bob can make this decision. But God put Chris on this earth for a very specific reason which has not yet been fulfilled. If Bob decides not to kill Chris it is within God's will, but if he decides to kill Chris than it is breaking God's will. If God's will can be broken by a simple human than God is not as powerful as He has led us to believe. If Bob decides to let Chris live and stays within God's will than God may be considered the powerful being written about but in that case Chris really didn't have the free will that he imagined.