Alexa Ray, Billy Joel's daughter, has been harassed for months by alleged cyber-stalker Sheryl Finley. Finley sent messages to Alexa that were terrifying enough that her dad turned to his pal Paul McCartney to hunt down the woman obsessed with his daughter. McCartney reccomended a private security firm called NetDefense based in Europe who weren't tied to the same legal restrictions as police, sources close to the family said. Alexa Ray was afraid to leave her Manhattan home and her supermodel mother, Christine Brinkley, was "terrified" her baby would be hurt, a source told the New York Post. This prompted her "Piano Man" dad to take action.

The investigators from Paul McCartney's referral were successful-- they nabbed the alleged stalker, Sheryl Finley, a 40-year-old woman, in January. She was buck-naked in the frigid woods near Austin, Minn when they caught her.

Court documents said Finley wrote Alexa more than 60 Facebook messages under the alias "Rick Steenfield" from computers in the Austin Public Library and a nearby community college. Several of the messages graphically described "pedophilia, sadistic-sexual behavior, violent physical assaults and murder." Finley spent months committed in a mental institution in 2010.

Finley pleaded "not guilty" to charges of felony stalking for electronic messages sent by false impersonation and gross misdemeanor stalking for repeated messages.

Sheryl Finley told investigators that the rape and murder she described in the messages were not goals for "during this life" and she remained hopeful that Alexa Ray would not "object to meeting with her." She has a pre-trial date of May 3^rd.

According to experts, celebrity stalkers are often propelled by delusion that they have a relationship to the famous person or that the famous person would want to have a relationship with them. Billy and Alexa Ray Joel declined to comment on the case.

Alexa Ray, 27, is working on her own music career, taking after her dad. She released an EP in 2006 and attended NYU.