Penn's studies at Lincoln's Inn were interrupted by the great plague that swept over London and devastated the city. Like most other people of means he left the place and went into the country, carrying with him memories of the sick and suffering in the wretched, ill-kept streets and alleys. He was lonely in the country, and he could not help remembering the scenes in the plague-stricken town; so that when his father came back and joined him, the Admiral found William again in his former speculative frame of mind. To once more divert his mind, Sir William sent him to enter the service of the Duke of Ormond, who, as Lord Lieutenant of Ireland, held quite a court in the city of Dublin. The Admiral was Governor of Kinsale, in County Cork, and William was given charge of his father's affairs there, as well as being employed in various ways by the Duke of Ormond. He enjoyed this work, and when there was a mutiny of the soldiers at Carrickfergus, he took a large part in quelling it, so pleasing the duke by his ability that the latter suggested that young Penn should be made captain of the Admiral's troop of soldiers. Sir William was glad to hear such good reports of his son, but did not think him fitted as yet to command his soldiers. Young Penn was enjoying life on his father's estate and at the duke's court in Dublin, and was decidedly the courtier and man of affairs; when one day, being in Cork on business, he happened to hear the preaching of Thomas Loe, a man he had already heard at Oxford. The message of that sermon lay in the words, "There is a faith which overcomes the world, and there is a faith which is overcome by the world." It made a deep impression on the young man. Was his faith of the type that overcomes the world? Or was it of the kind that is overcome by pride of place and fortune? He feared that thus far his faith had shown itself of the latter sort. He gave a great deal of thought to that message of Thomas Loe. Being so ardent by nature, he determined that his faith should overcome the temptations that surrounded him. He would fight by the side of those who believed in the simple teachings of early Christianity and who were unhampered by the forms and ceremonies the other churches had imposed upon their members. Thomas Loe's sermon was the spark that set Penn's zeal ablaze. He made up his mind to become a Quaker, in spite of all that his family or friends might say. The new faith had made its appeal to the deepest springs of his earnest and religious nature.