James Nesbitt as the NI killer dentist

The Secret, ITV's new four-part drama about a real-life crime in Northern Ireland, begins this Friday, 29 April 2016, at 9 pm.

It is based on the true story of how Sunday school teacher and respectable dentist Colin Howell (James Nesbitt) from Portadown and Hazel Buchanan (Genevieve O'Reilly) had an affair and planned the “perfect murder” to kill their partners and fake a suicide pact.

Major spoilers here.