On the afternoon of July 1, 1981, Los Angeles police responded to a distress call at 8763 Wonderland Avenue in Laurel Canyon and discovered a grisly quadruple homocide. Ron Launius (Lucas), Billy Deverell (Nelson), Barbara Richardson (Wagner) and Joy Miller (Garofalo) were found brutally murdered, bludgeoned to death with a pipe, and Launius's wife, Susan (Applegate), was left in critical condition.

The police investigation that followed -- led by detectives Sam Nico (Levine), Louis Cruz (Frankie G.) and Mike Peters (Gainey) -- would unearth a seedy world of drugs and violence, ultimately revealing a motley crew from L.A's underbelly including ex-con David Lind (McDermott), nightclub impresario Eddie Nash (Bogosian), and porn legend John Holmes (Kilmer) as well as Holmes's estranged wife Sharon (Kudrow) and his teenage lover Dawn Schiller (Bosworth).