Decker is a 42-year-old private investigator. He’s six-foot-five, 50 pounds overweight, with long hair, and a scraggly beard. In his younger years, he suffered a head injury as a professional football player that permanently altered the wiring of his brain. He has a condition called hyperthymesia, which means he never forgets, and has also become a synesthete who counts in colors. His social intelligence has been impaired so that he has difficulty relating to others. As a result, he prefers to isolate himself from normal human interaction.

Decker’s family has been brutally murdered, and he’s tortured by the recurring memories of the event. Because he can’t find any closure for this senseless tragedy, he helps investigate a mass shooting at his old high school in the hopes that he can give closure to someone else. 

Jamison is a reporter with the News Leader. She is in her late twenties—pretty, tall, and slim with bobbed brunette hair. Jamison initially tries to coerce a story out of Decker. He finds her manner intrusive and avoids her.

Though initially antagonistic, Jamison decides to help Decker investigate the shootings at Mansfield. Because her mentor was killed by the gunman, she has a personal stake in the outcome.