The family of Lisa Dorrian are set to appear on Crimewatch Live on Friday morning to make an "emotional appeal".
The 25-year-old was last seen alive on the night of Sunday, February 27, 2005 at a party in Ballyhalbert Caravan Park with police believing she was murdered that night or in the early hours of the morning.
For 20 years, her family have been fighting for answers and continue to appeal for information on her disappearance.
Read more: Lisa Dorrian "lost her life at the hands of people she knew and trusted"
Read more: Lisa Dorrian: PSNI release CCTV of 'last known footage' of 25-year-old
Crimewatch Live on BBC One sees hosts Rav Wilding and Michelle Ackerley asking for the public's help with unsolved cases.
The Police Service of Northern Ireland shared out a teaser clip for Friday's episode on social media, informing the public that the Dorrian family would be appearing on the show on Friday, March 21.
A spokesperson for the PSNI said: "Tomorrow’s Crimewatch Live will appeal for information on the disappearance and murder of Lisa Dorrian.
"Lisa, from County Down, was just 25 years old when she was murdered. Despite hundreds of search operations, the young woman’s body has never been recovered, and those responsible have yet to be held to account.
"Since that day her family have been fighting for answers, with Lisa's heartbroken mother passing away before ever finding out what happened to her beloved eldest daughter."
Watch the Crimewatch Live preview below...
Last month, the PSNI issued a renewed appeal for information, releasing the last known CCTV footage of Lisa, which shows her socialising in the days before her disappearance.
It is hoped this footage may "prick the conscience" of those who know what happened to her.
Ahead of their appearance, hosts Rav Wilding and Michelle Ackerley said: "In February 2005, Lisa Dorian disappeared from Co Down.
"Police believe she was murdered but the 25-year-old's body has never been found and no one has yet been brought to justice.
"On Friday's Crimewatch Live, Lisa's family will be here to make an emotional appeal for information to catch her killer and the detective leading the investigation will update on the latest developments in the case.
"Join us on Crimewatch Live BBC One at 10:45am."
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