In 1977, aspiring actress Christa Helm, who appeared in television shows such as "Wonder Woman" and "Starsky & Hutch," was found stabbed and bludgeoned to death in front of her agent's house. Now, 31 years after the case went cold, Helm's daughter and investigators sort through a twisted web of sex, celebrity and possible blackmail in the hopes of finally finding her killer. Helm was the classic small-town girl with big Hollywood dreams. Armed with her model-looks, the seductive blond left Milwaukee, Wis., and her daughter, eventually making her way to Hollywood. A fixture in the L.A. party scene, Helm was rubbing elbows with the rich and famous. Never at a loss for male attention, she kept company with a who's who of A-list actors and musicians including Warren Beatty, Jack Nicholson, Mick Jagger and even the Shah of Iran. In what many suspect was groundwork for blackmail, Helm kept a diary and even tape recordings of her star-studded sexcapades, both of which mysteriously disappeared after her murder. But Helm's sex life was not limited to celebrities. A special cold case squad recently uncovered a long string of boyfriends and girlfriends that Helm had left in her wake, sometimes having multiple affairs at the same time and possibly breeding jealousy among those involved. With many of Helm's friends now dead or missing, and other insiders refusing to talk, the case has hit numerous dead ends. Among those declining to speak with police is Tony Sirico, better known for his role as Paulie Walnuts on "The Sopranos," who investigators believe may have some useful information. Despite these obstacles, Helm's daughter and authorities remain undeterred in their quest for answers. Was Helm in over her head, murdered to shut her up? Was she the victim of a jealous lover? Or, was this simply a case of robbery? 48 Hours correspondent Maureen Maher reports.