Guest Stars Dominic MacHale as Sergeant Healy Demi Isaac Oviawe as Linda Walsh Jennifer Barry as Siobhan Walsh P.J. Gallagher as Principal Barry Walsh Shane Casey as Billy Murphy John Murphy as Guard Chris Kent as Conor's Dad Louis Slattery as Young Conor Ciaran McCarthy as Teenager Given Mask Joe Campff as Teenager Given Mask Dean Cronin as Passing Pupil Thomas McCarthy as Teenager with Knife Luke O'Driscoll as Teenager Ger Mullins as Teenager Luke Dunlea as Teenager Donal Cotter as Teenager Christopher O'Flaherty as Building Owner