Around 1570, O'Hurley left for Rome and it was during this time that he studied for the priesthood. In 1581 Pope Gregory XIII appointed him as Archbishop of Cashel. Due to illness O'Hurley did not return to Ireland until August 1583 when he arrived in Skerries. O'Hurley tried to keep his entry into the country secret from the English spies. The lord justices were altered to his arrival and they wanted to arrest O'Hurley as soon as possible.
After a short time in Meath, O'Hurley travelled to Carrick-on-Suir but, during his time there, the Baron of Slane travelled to meet him. The Baron was under pressure from the lord justices to arrest the Archbishop. When O'Hurley met the Baron of Slane, he agreed to go to Dublin, where he was interrogated in March 1584. After the first interrogation, O'Hurley had told the authorities nothing. They decided to torture him by roasting his feet in metal boots filled with oil. He was charged with treason but denied the charge. Archbishop O'Hurley was then condemned to death and hanged in Dublin on June 21st 1584.
In 1984, the then parish priest Fr Denis Browne unveiled a plaque in front of the church in Knockea to commemorate the 400th anniversary of the death of Dr. Dermot O'Hurley, Archbishop of Cashel.