The Beginning Always Starts the Same

Firstien's life is a simple one. He lost his wife to complications at birth, and has a reclusive fourteen year-old who likes to write his life away. When Firstien is killed by a serial killer, he finds out that his life is the pure reason for the world existing, and he is returned to the same day to fix the problems that have taken over the earth. How long can he keep this a secret? How long can he keep dying before it's too late for him to go back?