Book: Read any book concerning a man / woman of the cloth, a book about a character hiding a guilty secret or searching for absolution.
In Highly Illogical Behavior, Lisa befriends Solomon solely so she can cure him of his agoraphobia and use that to get into a college psychology program. She is naturally keeping this a secret from him. At first she feels no guilt whatsoever for what she is doing. However, as the story continues and she genuinely becomes friends with him, Lisa begins to grow guilty over what she is doing and the secret becomes a guilty one. I'm using the book to claim this door.