Crimmins

Crimmins is depicted in the book as evil. His photo in the journal is said to show a man who has piercing eyes with no mercy. People like him are the reason why McCaleb doesn't believe in god anymore. Crimmins was chased for long by McCaleb. At the time he was known as the code killer. But he had the constant feeling he was no one. Somehow he had to do something to become someone, so that people would actually care about him. And the one who mattered the most to him was McCaleb.

He wanted to matter to McCaleb. To do that, he could have killed him, but that was too easy. When he learned McCaleb was dying, he chose to save his life. That way, he thought he would always be part of McCaleb's life.

That is when he decided to kill for McCaleb. Then he did his best so that McCaleb would be the one investigating Gloria's case. What is more awful than investigating the death of a woman who was killed to enable you, though not intentionnaly, to live. That is pure devil !

Crimmins set things up so that McCaleb lives what he lived as he was the Code Killer, being chased.
He planned everything so that McCaleb would find out the killer was noone, that noone was the code Killer and that he had been played by him. He was probably hoping that McCaleb would be amazed at him, psychologically destroyed, and that he would have a place in his head for the rest of his days.