Mariska Hargitay's stepmother, Ellen Hargitay, shares in the "My Mom Jayne" documentary the story of what Jayne Mansfield once told her in a dream.

I couldn’t believe that this truth, this bombshell for me, didn’t ever come to light," says the ‘Law & Order: SVU’ star about going public with her biological father’s identity in an HBO documentary on her mother,