The final reveal is that O'Connor is not the father of the baby. In fact, Mackey is the father and he might not even be human. He is either the devil incarnate or a demon as evidenced by Gracie giving birth to snakes.
Sinister Minister: Reverend Enoch O'Connor who is a bible-thumping religious fanatic who keeps poisonous snakes with him. Ultimately subverted as he may be bible-thumping but he is on the side of right. Samuel Mackey who pretends to be tolerant is in fact extremely evil and might just be Satan himself.