A few yards from the centre of Edinburgh's leafy Dean Village, a noticeboard reflects the concerns of a neighbourhood steeped in historic significance. One poster gives details of a brass-rubbings trail along the riverside, another tells residents about a grant from Historic Scotland, while another advertises guided walks of the cobbled streets. Beloved by tourists, dog walkers, and Sunday afternoon escapists alike, on a sunny day when only the gentle rustle of leaves upsets the silence, this ''village'' in the heart of the city seems like a haven indeed.

But below the local notices, on a sheet of A4 held on with masking tape, is a police poster which hints at another story. The face of Louise Tiffney gazes out, a young woman, with fine features and shiny auburn hair, her mouth half open as if she did not expect to have her photo taken. She is missing, the poster says, having disappeared on May 27 from her home not 30 yards from this spot. Her family is becoming increasingly concerned for her welfare. What the poster does not say is that, six weeks into this investigation, police are having to consider the possibility that she may have been murdered.

That is not how it seemed at the beginning. Louise Tiffney, 43, went missing just four days before her 18-year-old son, Sean Flynn, was due to appear in court to admit causing the deaths of his cousin and his best friend in a car crash. It was feared then that the pressure of the court case and the grief of the accident might have proved to be too much for Ms Tiffney.

But since then, evidence has emerged that hints at darker possibilities, possibilities that 24 officers of Lothian and Borders Police are now investigating. A high-profile poster campaign failed to produce a call from the missing woman. Ten days after her disappearance, a diving unit from Central Scotland Police dredged a deep pool in the Water of Leith near her home, in case she had slipped and fallen in, to no avail. Then, at the beginning of last week, the case took an important turn following forensic tests. Based on the test results, police said they now feared Louise may be dead and were treating her disappearance as suspicious.

The tests were carried out on bloodstains found in a white Nissan Almera seen near Louise's home at the time of her disappearance. The DNA matched Louise's. The police received information about the car and traced it to an address in the city, but the owner, not thought to be a member of the Tiffney family, is not being viewed as a suspect.

News of the forensic results left her family devastated. But Detective Inspector Peter Avent, heading the inquiry, said it was essential to keep an open mind. ''Here we have a mother of a six-year-old on whom she doted. Probably every lady I've spoken to during this investigation has convinced me no mother would leave a six-year-old through choice.''

It had emerged that on the evening Louise disappeared, she had had an argument with her son. Sean Flynn has been questioned by police about his mother's disappearance, as have other members of the family. Her family, who have always insisted it was unlike her to vanish without explanation, are waiting anxiously for news. Many members of the wider public are also following this harrowing case, touched by the tragedy that has torn through this family like a quiet tornado.

Louise Tiffney, who used to work part time at a launderette in Stockbridge, Edinburgh, lived with her son and six-year-old daughter, Hannah, in Dean Path at the heart of Dean village. The community of Dean village is diverse, attracting those of modest means alongside the more affluent, as indicated by the juxtaposition of gleaming Ford Cougars and ageing Fiestas in the parking bays. Climbing roses cling to the half-timbered houses that rise up the steep southern bank, and thick vegetation shrouds the riverside walkways.

Dean bridge, infamous as the place from which a number of individuals have chosen to end their troubled lives, towers above. Louise's flat is one of several in a converted mill, erected in the early nineteenth century, which sits right on the edge of the glassy Water of Leith, just before it plunges over a weir.

Neighbours describe Louise and her family as fairly quiet. But there was turbulence beneath the surface. In January 2001, the family was struck by tragedy when Sean Flynn, then 17, was involved in a car accident that resulted in the death of his cousin, Paul Ross, and a friend, Christopher Magee, both 18. Flynn, who later got a driving licence, did not have one at the time, nor insurance.

On Friday, May 31, in the High Court in Edinburgh, Flynn admitted causing their deaths by dangerous driving. It emerged in court that he had bought an E-registered BMW 3-series car for (pounds) 960 just hours before the accident. Apparently ''determined to show off his new car'', Flynn stopped at a garage for petrol and took the opportunity to pursue a Ford Escort which had pulled out of the service station ahead of him, overtaking the car on the approach to a bend in Mid Calder, West Lothian.

As the car sped along at between 58mph and 80mph in a 30mph zone, Ross and Magee shouted at Flynn to slow down and he braked, at which point the car went out of control, hit a lamppost, overturned and went on fire. Flynn and the front-seat passenger, Mario Gagliardini, escaped with minor injuries. Ross and Magee, who were in the back seat, both died.

Flynn, described by the judge as ''of a good background and a hard-working student'', admitted the offence and was later sentenced to three years and nine months in a young offenders' institution.

The families of his victims had conflicting views on the sentence. Gerald Magee and his wife, Aileen, parents of Christopher Magee, felt the sentence was not harsh enough. But Lulu Tiffney, 41, Louise's sister and the mother of the other victim, said in a statement read out by her nephew's defence team that she did not blame or hate Sean, who had had a ''very

special relationship'' with her son.

It was a harrowing experience for all concerned. But Sean Flynn's mother was present neither at his trial nor his sentencing. The last time she had been seen was at midnight on Monday, May 27.

She left behind bank cards, keys, and cash. But above all, she left behind her beloved daughter, Hannah.

Three weeks ago, photographers and journalists crammed into a poky room at Torphichen Street police

station in the west end of Edinburgh where Hannah emerged before the cameras, along with her aunt and grandmother, in an appeal for help in tracking down her mother. Louise, according to her family, was Hannah's world. The six-year-old sat quietly - beside her aunt, Lulu, and her grandmother, Mary Tiffney, 70, who lives in Edinburgh with her husband, Robert - a bewildered little girl, tiny beneath the flashbulbs.

Shaking her head when asked if she wanted to say anything to the assembled press, she listened while her grandmother described how the little girl had been getting presents ready for her mother's return. ''I have told her that her mummy is missing and that we hope she comes home soon,'' said Lulu. ''I can't tell her anything else. She seems to have accepted that. We are just making wishes.''

Ms Tiffney said the family was ''baffled'' by Louise's disappearance, saying: ''We all miss you and love you. Please come home. If you are staying with someone, just give us a ring. We will understand.''

The forensic results, coming after days of silence, have raised expectations that this strange, sad case might be nearing a resolution. Police have had several calls linked to the car. But DI Avent, insists that, as yet, there is no positive line of inquiry and everything is ''up for grabs''.

He concedes that the absence of, at best, any recent sightings of Ms Tiffney or, at worst, a body, has been problematic. ''It makes it extremely difficult,'' he says. ''The focus of the investigation is still to find Louise, that is number one, and we still want to hear about anyone who might have seen the car in suspicious circumstances. Many people have phoned us, but I'm still making that appeal for information.''

Back in Dean village, Mrs Tiffney's neighbours have reacted with shock to the latest turn in the investigation. ''It was bad enough her going missing, that was a mystery,'' said one. ''But now it seems there's more to it. It really is awful.''

The wait for news, her many wellwishers must hope, cannot be long now.

Anyone who saw a white Nissan Almera in suspicious circumstances in the area of Dean Path or any other part of the country on the evening of May 27 or 28 is urged to contact the incident room at Livingston Police Station on 01506 431200 or Crimestoppers on 0800 555 111.