: Clara is revealed as a delusional serial arsonist who believes the number three has protective or spiritual significance. Her "compulsion" drove her to ensure everything occurred in sets of three, leading to the intentional deaths of those she believed "unbalanced" her rituals. Character Development
: The breakthrough comes when Dr. Spencer Reid identifies a ritualistic behavior. He recalls a science lab assistant, Clara Hayes , who displayed obsessive-compulsive traits, specifically counting in threes. [S1E2] Compulsion
"Compulsion" also deals with the psychological aftermath of the pilot episode for : : Clara is revealed as a delusional serial