Evil for the French novelist François Mauriac was necessary to tell stories of hope and love and redemption. Stories of childhood and innocence also required to be stories of evil and violence. But it is not the easy, cookie-cutter projection of evil prevalent among characters today (ie. bad guys in movies).
Evil is a mystery. How does the Christian storyteller understand this mystery? Mauriac wrestles with this question in his 1952 Nobel Prize in Literature speech:
For a Christian, evil remains the most anguishing of mysteries. The man who amidst the crimes of history perseveres in his faith will stumble over the permanent scandal: the apparent uselessness of the Redemption.
The well-reasoned explanations of the theologians regarding the presence of evil have never convinced me, reasonable as they may be, and precisely because they are reasonable. The answer that eludes us presupposes an order not of reason but of charity.
It is an answer that is fully found in the affirmation of St. John: God is Love.
Nothing is impossible to the living love, not even drawing everything to itself; and that, too, is written.