Police are convinced Margaret Fleming – who had learning difficulties – has “come to harm”.
Margaret, 36, was last seen by anyone other than the couple who were her official carers on December 17, 1999.
Carers Avril Jones, 57, and Edward Cairney, 75, told police she had a secret double life that she would not discuss with them.
The probe was initially a missing person inquiry but has been taken over by senior detectives from the Police Scotland Major Investigation Team, who track down murderers.
Officers have scoured Mr Cairney and Ms Jones’ bungalow at Inverkip, where they say Margaret was living since they took her in in 1997.
Police visited the property with social services officials following an application for an enhanced carers’ allowance, but they were told that Margaret was unavailable. She was reported missing later the same day, October 28.
Senior insiders say the officers in charge of the inquiry are reluctant to declare the disappearance a “probable murder” until they have exhausted every other possibility.
One said: “I can understand their position, not wanting to jump the gun, and that makes perfect sense.
“However, it is now patently obvious that something has happened to this poor woman. Whether she has suffered an accident or met foul play is clearly unknown. Investigating officers have applied every proof of life test to this case and she has failed them all.
“There have been no independent sightings, no work records, GP appointments, dealings with social workers, contact with friends, family or anyone else for that matter.”
She added: “Taking the next step and declaring she is believed to be dead is a major move and shifts focus from the search for Margaret to potential suspects.
“The inquiry is being handled in a textbook manner and there are other forces at play, including the procurator fiscal and the Crown Office.
“Stating that she is believed to be dead puts more pressure on the inquiry officers who have meticulously investigated every aspect of this woman’s life.”
To mark the 17th anniversary of the last known sighting of Margaret, on Saturday, Detective Chief Inspector Paul Livingstone, the Senior Investigator Officer, said: “If Margaret is reading this, I would ask her to get in touch with police.
She is not is any trouble, we just want to ensure she is safe and well.”
Source : EXPRESS