Consider the following instance of the great mercy of Mary.
In the year 1604, in a city in Belgium, there were two young students who gave themselves up to a life of debauchery instead of following their studies.
One night they were at the house of an evil woman; but one of the two, who was named Richard, stayed only a short time and then returned home. While he was preparing to retire, he remembered that he had not yet said the few Hail Marys that were his daily practice.
He was very tired and half inclined to omit them; nevertheless, he forced himself through the routine, saying the words half asleep and with no particular devotion. Then he lay down and fell asleep.
Suddenly he was wakened by a violent knocking at the door. The door was closed, but the figure of a young man, hideously deformed, passed through it and stood before him.
"Who are you?" Richard cried. "You do not know me?" asked the other. "Ah yes, now I do," said Richard; "but how changed, with all the appearance of a devil!"
"Alas, unhappy creature that I am," said his companion, "I am damned! When I was leaving that house of sin, a devil came and strangled me. My body lies in the street; my soul is in Hell.
"And know this --- the same fate awaited you, except that the Blessed Virgin spared you for that little act of homage of the Hail Marys. If you are not a fool, profit by this warning which the Mother of God has sent." He then opened his mantle, showing the flames and serpents by which he was tormented, and disappeared.
Breaking into a flood of sobs and tears, Richard went down on his knees to give thanks to Mary his protectress. Then as he pondered how to change his life he heard the bell of the Franciscan monastery ringing for matins. "It is there," he said, "that God calls me to do penance."
He went immediately to the monastery and begged the Fathers to admit him. Since they knew his wicked life, they were hardly willing to do so. But sobbing bitterly, he told them all that had happened. And when two Fathers had been sent to the street and had found the strangled body, which was charred and blackened, they admitted him.
From that time on he led an exemplary life and at length went to preach the Gospel in India, and thence to Japan. There he had the happiness of giving his life for Jesus Christ, being burnt alive for the faith at Nagasaki on September 10, 1622.
Taken from The Glories of Mary