One of my favorites stories is the one about Saint John the Apostle restoring a sinful young man. Saint John committed a young man to a Catholic priest for instruction and baptism. However, the youth fell away and became a highway robber. When Saint John learned of this, the elderly apostle asks for a horse and goes riding into the hills to find the lost youth.
The youth, seeing the sorrowful Apostle, slumps and begins to weep. Saint John restores the young man to communion with the Church. A wonderful story.
It reminds us that Saint John was the Apostle of Divine Mercy because he alone rested his head on the Sacred Heart during the first Eucharist and he alone stood with Mary as the blood and water flowed from the Sacred Heard of the Son of God. The story below testifies to the Apostle's intimate knowledge of the Divine Mercy of Christ.
The tale is found at the end of Saint Clement of Alexandria's work Who is the Rich Man That Can Be Saved? (available here via NewAdvent.org)
"And that you may be still more confident, that repenting thus truly there remains for you a sure hope of salvation, listen to a tale, which is not a tale but a narrative, handed down and committed to the custody of memory, about the Apostle John. For when, on the tyrant's death, John returned to Ephesus from the isle of Patmos, he went away, being invited, to the contiguous territories of the nations, here to appoint bishops, there to set in order whole Churches, there to ordain such as were marked out by the Spirit.
"Having come to one of the cities not far off (the name of which some give ), and having put the brethren to rest in other matters, at last, looking to the bishop appointed, and seeing a youth, powerful in body, comely in appearance, and ardent, said, This (youth) I commit to you in all earnestness, in the presence of the Church, and with Christ as witness. And on his accepting and promising all, he gave the same injunction and testimony. And he set out for Ephesus. And the presbyter taking home the youth committed to him, reared, kept, cherished, and finally baptized him. After this he relaxed his stricter care and guardianship, under the idea that the seal of the Lord he had set on him was a complete protection to him. But on his obtaining premature freedom, some youths of his age, idle, dissolute, and adepts in evil courses, corrupt him. First they entice him by many costly entertainments; then afterwards by night issuing forth for highway robbery, they take him along with them. Then they dared to execute together something greater. And he by degrees got accustomed; and from greatness of nature, when he had gone aside from the right path, and like a hard-mouthed and powerful horse, had taken the bit between his teeth, rushed with all the more force down into the depths. And having entirely despaired of salvation in God, he no longer meditated what was insignificant, but having perpetrated some great exploit, now that he was once lost, he made up his mind to a like fate with the rest. Taking them and forming a band of robbers, he was the prompt captain of the bandits, the fiercest, the bloodiest, the cruelest.
"Time passed, and some necessity having emerged, they send again for John. He, when he had settled the other matters on account of which he came, said, Come now, O bishop, restore to us the deposit which I and the Saviour committed to you in the face of the Church over which you preside, as witness. The other was at first confounded, thinking that it was a false charge about money which he did not get; and he could neither believe the allegation regarding what he had not, nor disbelieve John. But when he said I demand the young man, and the soul of the brother, the old man, groaning deeply, and bursting into tears, said, He is dead. How and what kind of death? He is dead, he said, to God. For he turned wicked and abandoned, and at last a robber; and now he has taken possession of the mountain in front of the church, along with a band like him. Rending, therefore, his clothes, and striking his head with great lamentation, the apostle said, It was a fine guard of a brother's soul I left! But let a horse be brought me, and let some one be my guide on the way. He rode away, just as he was, straight from the church. On coming to the place, he is arrested by the robbers' outpost; neither fleeing nor entreating, but crying, It was for this I came. Lead me to your captain; who meanwhile was waiting, all armed as he was. But when he recognized John as he advanced, he turned, ashamed, to flight. The other followed with all his might, forgetting his age, crying, Why, my son, do you flee from me, your father, unarmed, old? Son, pity me. Fear not; you have still hope of life. I will give account to Christ for you. If need be, I will willingly endure your death, as the Lord did death for us. For you I will surrender my life. Stand, believe; Christ has sent me.
"And he, when he heard, first stood, looking down; then threw down his arms, then trembled and wept bitterly. And on the old man approaching, he embraced him, speaking for himself with lamentations as he could, and baptized a second time with tears, concealing only his right hand. The other pledging, and assuring him on oath that he would find forgiveness for himself from the Saviour, beseeching and falling on his knees, and kissing his right hand itself, as now purified by repentance, led him back to the church.
"Then by supplicating with copious prayers, and striving along with him in continual fastings, and subduing his mind by various utterances of words, did not depart, as they say, till he restored him to the Church, presenting in him a great example of true repentance and a great token of regeneration, a trophy of the resurrection for which we hope; when at the end of the world, the angels, radiant with joy, hymning and opening the heavens, shall receive into the celestial abodes those who truly repent; and before all, the Saviour Himself goes to meet them, welcoming them; holding forth the shadowless, ceaseless light; conducting them, to the Father's bosom, to eternal life, to the kingdom of heaven.