More than 30 years ago, 17-year-old Robin Murphy vanished after meeting up with a friend at a New York shopping center where she worked.

"I got the call. I was at work. And they said my sister never came home. And I got a gut feeling something was wrong. I felt something was off," Jamie Murphy said of his younger sister's disappearance in a new interview with "20/20." The Carmel, New York, teen's April 9, 1995, disappearance remains a mystery to family, friends and law enforcement.

A new "20/20" episode, "Hiding Beneath The Surface: The Putnam County School Girls" airing Friday, Nov. 13, at 9 p.m. ET on ABC and streaming the next day on Disney+ and Hulu, follows correspondent John Quiones as he examines multiple cases.