Based in Quantico, Virginia, the Behavioural Analysis Unit (BAU) is a subsection of the FBI. Called in by local police departments to assist in solving crimes of a serial and/or extremely violent nature where the perpetrator is unknown (referred to by the Unit as the unknown subject or unsub for short), the BAU uses the controversial scientific art of profiling to track and apprehend the unsub. Profiling entails coming up with basic characteristics of the unsub and the victims (referred to as the victimology), using evidence from the case and matching that information to historic precedents and psychological analyses as a means to solve the case. Because of the nature of the work conducted by the BAU--the work being time consuming and psychologically demanding--its members are fiercely loyal to the Unit and to its other members. Also because of the work's overall demanding nature, not many members of the BAU have been able to maintain a happy or stable family life.