DETECTIVES BELIEVED A 13-YEAR-OLD GIRL WHO VANISHED FROM HER CALIFORNIA HOME IN 1981 WAS MURDERED - BUT YEARS LATER A WOMAN TURNED UP CLAIMING TO BE THE MISSING GIRL - WAS SHE AN IMPOSTER?

"48 Hours" Reports in "What Ever Happened to Mary Day?"

10:00 PM, ET/PT - Mary Day was 13 years old in 1981 when she vanished from her family's Seaside, Calif., home. What's shocking is that there is no record of her parents ever reporting her missing. Years later, after her sister got police on the case, they believed Day was murdered. But then there was a turn no one saw coming. Maureen Maher and 48 HOURS investigate the strange case of the missing teenager, the police investigation years later, and a woman in Arizona who claimed to be her, in an encore of "What Ever Happened to Mary Day?" to be broadcast Saturday, Dec. 23 (10:00-11:00 PM, ET/PT) on the CBS Television Network and streaming on Paramount+.

48 HOURS is broadcast Saturdays at 10:00 PM, ET/PT on CBS, and streams anytime on Paramount+. You can also watch 48 HOURS on the CBS News Streaming Network Wednesdays at 8:00 PM, ET. 48 HOURS is also available on CBSNews.com, Fave TV, Pop TV, Pluto US, Pluto UK, Pluto Nordics, Pluto Canada and Pluto South Africa. Download the CBS News app on your phone or connected TV. Follow 48 HOURS on Twitter, Facebook and Instagram. Listen to podcasts at CBS Audio.