Guest Stars Lydia McGuinness as Peggy Mahon Brian McCardie as James Connolly Steve Wall as Detective Coleman Millie Donnelly as Gracie Mahon Jaelynne Wallace Ruane as Sadie Mahon Jordanne Jones as Minnie Mahon Gus McDonagh as Monsignor Mulcahy Michael Feast as Sir Matthew Nathan Barry Keoghan as Cormac McDevitt Marcus Lamb as Patrick Pearse Niamh Cusack as Nellie Cosgrave Joanne Brennan as Dr. Kathleen Lynn Jason Cullen as Peter Mahon Ryan McAllister as Sylvester the Butler Lalor Roddy as Thomas Clarke Ruairí Heading as Fusilier McGarry Jack Shepherd voices General William Lowe Sean Fox as Sean McDermott Kieran O'Reilly as Captain Robert Barton Camille O'Sullivan as Countess Constance Marklevicz Ann Skelly as Biddy Lambert John Connors as Michael Molloy Adrian Hudson as Lofty Lloyd Barry Barnes as Constable James O'Brien Brendan McCormack as DMP Sergeant Lynn Rafferty as Prostitute