It was just about this time that the excessive heat of the summer of 1466 caused the outbreak of that great pestilence which carried off more than forty thousand people in the jurisdiction of Paris，among others，says Jean de Troyes，'M re Arnoul，the King's astrologer，a right honest man，both wise and merry withal.'The rumour spread through the University that the Rue Tirechappe had been specially devastated by the malady.It was here，in the middle of their fief，that Claude's parents dwelt.Much alarmed，the young student hastened forthwith to his father's house，only to find that both father and mother had died the previous day.An infant brother，in swaddling-clothes，was still alive and lay wailing and abandoned in the cradle.This was all that remained to Claude of his family.The young man took the child in his arms and went thoughtfully away.Hitherto he had lived only in the world of Learning；now he was to begin living in the world of Life.
This catastrophe was a turning point in Claude Frollo's existence.An orphan，an elder brother，and the head of his house at nineteen，he felt himself rudely recalled from the reveries of the school to the realities of the world.It was then that，moved with pity，he was seized with a passionate devotion for this infant brother.How strange and sweet a thing this human affection to him，who had never yet loved aught but books！
This affection waxed strong to a singular degree；in a soul so new to passion，it was like a first love.Separated since his childhood from his parents whom he had scarcely known；cloistered and immured，as it were，in his books，eager before all things to study，to learn；attentive hitherto only to his intellect which expanded in science，to his imagination which grew with his literary studies，the poor scholar had not yet had time to feel that he had a heart.This young brother，without mother or father，this helpless babe，suddenly fallen from the skies into his arms，made a new man of him.He perceived for the first time that there were other things in the world besides the speculations of the Sorbonne and the verses of Homer；that Man has need of the affections；that life without tenderness and without love is a piece of heartless mechanism，insensate，noisy，wearisome.Only，he imagined，being as yet at the age when one illusion is replaced merely by another illusion，that the affections of blood and kindred were the only ones necessary，and the love for a little brother was sufficient to fill his whole existence.
He threw himself，therefore，into the love of his little Jehan with all the passion of a character already profound，ardent，and concentrated.The thought of this poor，pretty，rosy，golden-haired creature，this orphan with another orphan for its sole support，moved him to the heart's core，and like the earnest thinker that he was，he began to reflect upon Jehan with a sense of infinite compassion.He lavished all his solicitude upon him as upon something very fragile，very specially recommended to his care.He became more than a brother to the babe：he became a mother.
Little Jehan having still been at the breast when he lost his mother，Claude put him out at nurse.Besides the fief of Tirechappe，he inherited from his father that of Moulin，which was held of the square tower of Gentilly.It was a mill standing upon rising ground，near the Castle of Winchestre，the present Bicêtre.The miller's wife was suckling a fine boy at the time；the mill was not far from the University，and Claude carried his little Jehan to her himself.
Thenceforward，feeling he had a heavy responsibility on his shoulders，he took life very seriously.The thought of his little brother not only became his recreation from study，but the chief object of those studies.He resolved to devote himself wholly to the future of that being for whom he was answerable before God，and never to have any other spouse，any other child than the happiness and welfare of his little brother.
He bound himself，therefore，still more closely to his clerical vocation.His personal merits，his learning，his position as an immediate vassal of the Bishop of Paris，opened wide to him the doors of the Church.At twenty，by special dispensation from the Holy See，he was ordained priest，and as the youngest of the chaplains of Notre-Dame，performed the service at the altar called，from the late hour at which the mass was celebrated there，altare pigrorum—the sluggards'altar.
After this，and because he was more than ever immersed in his beloved books，which he only left to hasten for an hour to the mill，this union of wisdom and austerity，so rare at his age，had speedily gained him the respect and admiration of the cloister.From the cloister his fame for erudition had spread to the people，by whom，as frequently happened in those days，it had been converted in some sort into a reputation for necromancy.
It was just as he was returning on Quasimodo-Sunday from celebrating mass for the sluggards at their altar—which was beside the door in the choir leading into the nave，on the right，near the image of the Virgin—that his attention had been arrested by the group of old women chattering round the foundling.
He accordingly drew nearer to the poor little creature，the object of so much abhorrence and ill-will.The sight of its distress，its deformity，its abandonment，the remembrance of his young brother，the horror that suddenly assailed him at the thought that if he were to die his beloved little Jehan might thus be miserably exposed upon the selfsame bed—all this rushed into his mind at once，and，moved by an impulse of profound compassion，he had carried away the child.