When ordinary law enforcement is not enough, assistant chief Joseph Armstrong (David) and his secret police force, the S.I.S. (Special Investigation Squad), step in to hunt down major criminals on the streets of Los Angeles and bring them to justice. This covert branch of the LAPD tracks the most dangerous, habitual offenders and attempts to catch them in the act of committing violent crimes. Until now, S.I.S.’s unheralded work has been shrouded in secrecy but their controversial methods begin to face closer scrutiny from police brass when they track a notorious, volatile killer who is wreaking havoc across the city. Melville Atkinson (Nable), Billy Beckett (Stebbings), Donovan Rivers (Hardwick) and Jayne Sorenson (Porch) make up this elite tactical squad and for them, failure is never an option.