Detectives who charged a dentist and his ex lover with the murders of their former partners are investigating a third death, it was revealed today.
Retired company director Henry Clarke collapsed just days before the bodies of his daughter and a policeman were found outside his holiday home in Castlerock, Co Derry nearly 18 years ago.
It is believed he suffered a heart attack or some sort of seizure, but the circumstances and cause of his death are now under fresh examination, according to sources close to the double murder inquiry.
Twelve days after he died in May 1991, the bodies of his daughter Lesley Howell, 31, and RUC officer Trevor Buchanan, 32, were found in a car filled with exhaust fumes, victims of an apparent suicide pact, after finding out that their partners were having a secret affair.
All were members of the Baptist Church in the Coleraine, Co Derry area where they lived at the time.
Late last month however, dentist Colin Howell, 49, and Constable Buchanan's wife, Lesley Stewart, 45, (she later re-married) were charged with the murders, and Howell is also facing a series of further accusations that he drugged and indecently assaulted women. He specialised in dental implants at his clinic in Ballymoney, Co Antrim.
The Police Service of Northern Ireland refused to comment on the new twist to the inquiry which is set to widen dramatically as detectives delve deeper into the dentist's private life and financial affairs.
A spokesman said: "It would be inappropriate to comment on the detail of the investigation."
The bodies of Mrs Howell and Constable Buchanan were found in a blue Renault estate inside a garage at the back of the holiday home of Mrs Howell's late father in a row of cottages known as the Twelve Apostles.
She was lying heavily made up in the back seat wearing headphones from a personal music stereo and listening to a gospel tape.
A pipe from a vacuum cleaner was attached to the exhaust, passed under a tailgate and in through an open window beside Mrs Howell's head. Constable Buchanan was in the front seat, and both clutched photographs of their children.
A Coroner's Court inquest later ruled both died from suicide as a result of carbon monoxide poisoning.
Apart from his house at Castlerock, it is understood Mr Clarke owned property in Hillsborough, Co Down. His daughter met Howell when she worked as a nurse at the City Hospital in Belfast and married two years later in the summer of 1983.
They had four children. Two years ago their eldest Matt, 22, a student, fell 40 feet from a balcony to his death in St Petersburg, Russia, where he was on a languages placement course.
Howell later remarried and lived with his American-born wife Kyle until just before Christmas, but had moved out of the family home to live in a caravan park in Castlerock.
As part of the murder investigation police are expected to exhume the bodies of Mrs Howell and Constable Buchanan. Mr Clarke was cremated.
A financial expert has been called in to examine the dentist's affairs amid reports he suffered heavy losses in a failed overseas pyramid scheme which left him with severe money difficulties. He had sold his interests in the dental practice in Ballymoney as well as one in Bangor, Co Down.
Police are to trace as many of his former patients as they can. Names, addresses and appointments lists have been checked and at least 200 letters are to be sent out in the next couple of days asking them if they can assist with the investigation.
When asked if the investigation team was taking steps to interview other former patients of Howell, the spokesman added: "This named individual is under investigation. He has been charged with a number of serious offences. It would be inappropriate for police to comment further at this time due to the ongoing investigation and future court proceedings."
Howell is in custody, but Stewart, who later re-married a senior police officer, is out on bail.
She is due to appear at a remand hearing in Coleraine on April 6.