The past comes back to haunt DCI Mathias as he 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. However, Independent investigator John Powell is on the cusp of ruling Iwan's death as a suicide - could this change things? With mounting pressure on him coming from all directions to close the case will Mathias toe the line or will he risk everything in pursuit of the truth?