New evidence has emerged which may help detectives solve a crime which has remained a mystery for more than two decades.
Sally Ann John disappeared when she was working as a sex worker in Swindon in September 1995.
Police are treating this as murder.
However, despite possible links to double killer Christopher Halliwell, no one has ever been charged with Sally's murder, and her body has never been found.
In 2015, three men were arrested on suspicion of kidnap and murder and later bailed.
Tonight, the case is being featured on BBC 1's Crimewatch where it will reveal a postcard allegedly sent by Sally Ann John after she went missing.
Police say this postcard was written by someone else, possibly a murderer trying to cover his tracks.
A reward of £25,000 is being offered for information which leads to the discovery of her body or secures a conviction at court.
Sally Ann's mother Lesley told the programme: "It's a horrible feeling that your daughter may have been murdered or has been murdered because you can't do anything about it, you can't do anything."
"I just want her found, I really do want her found and whoever did this to be counted for."