DCI Mathias investigates the death of Catrin John, convicted killer and former resident of the Pontarfynach Children's Home. As Mathias and Mared investigate Catrin's death, they begin to suspect it might be linked to the death of former police officer Iwan Thomas. As Mathias delves deeper into the past, the pressure on him to close the case increases. Will Mathias toe the line or will he risk everything in pursuit of the truth?
Aired: 11 Dec 2016