Let This Be Our Secret is a remarkable true crime story set on Ireland's north coast where the bodies of a couple were found in a car filled with carbon monoxide fumes - the apparent victims of a suicide pact.

But 18 years later, wealthy dentist Colin Howell confessed to police that it was he and his then lover, Hazel Buchanan, who murdered their respective partners. All four belonged to Coleraine Baptist Church. Howell later re-married an American divorcee, while Buchanan, a mother of two, eventually began a new life with a senior policeman who was once a staff officer to the former RUC Chief Constable Hugh Annesley. Howell went on to run hugely successful dental implant surgeries in Ballymoney, Co. Antrim and Bangor, Co. Down, but despite his strong Baptist beliefs, he lived a secret life of lust, deceit, and greed. It was to prove to be his undoing when his life unraveled spectacularly at Christmas 2008 with heavy overseas investment losses linked to a project to find Japanese gold hidden in the Philippines. And he has admitted other affairs and sexual advances to his dental patients. Hazel Buchanan, Howell's ex-lover, also re-married. She emerged as a high-maintenance and glamorous keep-fit fanatic who according to friends always had a haunted look, fearing that sooner or later an investigating police officer would one day tap her on the shoulder. Out of Northern Ireland's dark and troubled history has emerged a crime like no other.