Tenth century Ireland is a collection of feudal kingdoms at the edge of the known world, ruled by warlords and clerics. A young boy, the bastard son of an abbot, is taken from his mother and sent to live out his life in a remote monastery. A hideously deformed monk befriends him and becomes his mentor but ten years later, Dermot is forced to leave his friend and the monastery behind. A series of sudden, tragic deaths results in a crisis of faith and sets him on a soul-searching journey that will take him from the hallowed halls of Rome to the blood-soaked battlefields of his turbulent homeland. Brian Boru's campaign for absolute control of Ireland is gaining momentum and Dermot seizes it as an opportunity to satisfy his own ambitions. He gives Boru his backing but the bloody battles that ensue cause Dermot to recall the lessons his mentor taught him years before and he finds himself fighting his own demons in a desperate attempt to rediscover his true self. Thy Kingdom Come brings to life the political and religious landscape of Mediaeval Ireland, where royal courts seethe with political intrigue and tenuous alliances and where warlords and churchmen play a dangerous game of loyalties and betrayal.