Detective Sonya Cross, is a member of the El Paso police department who has Asperger syndrome.
Her sister Lisa Cross was killed when Sonya was 15. Sonya still visits her, now brain damaged, murderer and keeps his drawings on the fridge - maybe to try and find out why he killed her sister.
Hank Wade is Sonya's boss and mentor, often giving her advice on how to behave around people.
Marco Ruiz is Sonya's partner. In the beginning she didn't trust him and considered him unprofessional for talking to his wife while at work and letting an ambulance drive through a crime scene.