Portents were not confined to Rome. According to Evagrius,[136] a great earthquake in a.d. 589 laid Antioch in ruins, destroying the sanctuary of the Mother of God, and taking sixty thousand lives. In Upper Italy also there were extensive inundations due to overflowing of the mountain streams in Venetia, Liguria, and the sub-Alpine plains.

It is instructive to contrast the records of these chroniclers of the Church of the West with those of Procopius and Evagrius, and still more so with that of the pagan historian Thucydides. So intent are they on the mental and moral features of the distemper, that they say almost nothing of its physical features. They dilate at length on the visions and hallucinations that haunted the distracted fancy of the sufferers, which Thucydides disregards, though such must have accompanied the wild delirium he describes. Demons stalking the streets, ineffaceable marks and moulds on houses, voices from the grave, and celestial portents were the creations of the delirious fancy, and are faithfully reproduced in the pages of the Christian writers. One is sensible of something of the spirit in which Fra Angelico portrayed the joys of heaven and the torments of hell, when pestilence lay heavy on mediaeval Italy. The mortality in Rome was appalling. Death was rampant everywhere. At first the dead bodies were gathered up and flung in loads into great gaping graves, but after a while none were left even to bury the dead, and putrid corpses littered the streets. All business was at a standstill, and such as survived were huddled, panic-stricken like sheep, in the insecure sanctuary of the churches. To add to the general consternation, Pope Pelagius perished on February 8, a.d. 590. The choice of a successor lay with the clergy and people of Rome, subject to confirmation by the Emperor. With one accord they haled Abbot Gregory from the seclusion of his monastery to the pontifical chair in anticipation of the Imperial assent. Gregory of Tours, Paul the Deacon, and John the Deacon all tell of Gregory’s unwillingness to obey the summons, and of his attempt to intercept the letter of election on its way to the Emperor in Constantinople. But meantime, as the plague showed no sign of abating, Gregory determined to try to appease the wrath of God by a special act of contrition. Ascending the pulpit of St. John Lateran, he preached a memorable sermon, which has been preserved by the hand of Gregory of Tours. He implored them to make their sufferings an instrument for their conversion, and a means by which to soften the hardness of their hearts. He besought them, as Cyprian had done before, as Borromeo and Belsunce were to do hereafter, not to let the suddenness with which death seized them, sweeping away numbers at a time, and giving no opportunity for tears of penitence, find them unprepared to meet their God. Let them call their sins to mind and purge them away with weeping, for God wills not the death of a sinner, but rather that he may turn from his wickedness and live. Let no man despair because of the multitude of his offences. Did not God forgive the people of Nineveh of old, when they did penance for three days, and did He not give the reward of everlasting life to the dying thief? Let them therefore turn with him to God with importunity of prayer, or ever the sword of punishment descend. Does He not say by the mouth of the Psalmist: call upon Me in the time of trouble: so will I hear thee and thou shalt praise Me. Let them all come with contrite hearts and mended moods at early dawn on the fourth day from then to the celebration of a sevenfold litany, and with lamentation in their souls, so that the stern Judge may remit the sentence of damnation He has purposed to pass upon them. Let the clergy then start from the church of the martyr-saints Cosmo and Damian, along with the priests of the sixth region. All the abbots with their monks from the church of the martyrs Gervase and Protasius, along with the priests of the fourth region. All the abbesses with their flocks from the church of the martyr-saints Marcellinus and Peter, along with the priests of the first region. All the children from the church of the martyr-saints John and Paul, along with the priests of the second region. All the laity from the church of the protomartyr-saint Stephen, along with the priests of the seventh region. All the widowed women from the church of St. Euphemia, along with the priests of the fifth region. And the married women from the church of the martyr-saint Clement, along with the priests of the third region. Let them all go forth from these several churches with prayer and lamentation, to meet at the basilica of the Blessed Virgin Mary the Mother of Christ, there with long and earnest supplication to implore pardon for their sins.

So Gregory distributed the remnant that the plague had spared according to the seven ecclesiastical regions of Rome, bidding his clergy spend the three days’ interval in ceaseless psalms and prayers for mercy. Then on the fourth day, the festival of St. Mark, in the pale light of the early April morning, the great procession set out. With solemn chant of doleful Miserere, these seven trains of human suffering wended their slow way sadly amid the ruined monuments of ancient Rome. No other sound broke the stillness, but the faint rustle of sweeping garments and the silent shuffle of sick men’s feet. Now and again one fell stricken and lay as he fell, for Death was moving hither and thither among the moving ranks.[137] No less than eighty breathed out their lives before the church of the Mother of God was reached. There again Gregory fervently exhorted the people to repentance, so that the plague might cease.

A legend has it that as Gregory, heading his train of penitents, reached the Aelian Bridge, there, right before him, on the summit of Hadrian’s mole, a heavenly vision met his eyes. There stood the Archangel Michael, restoring a flaming sword to its sheath, in token that the plague was stayed. It is to this legend that the mausoleum owes the name of Castel S. Angelo, that it has borne since the tenth century at least. A bronze figure of the Archangel sheathing his sword still hovers on the summit, fifth of a series that have stood there at different times.

The legend of the angel is not mentioned by either of Gregory’s biographers, the deacons Paul and John, or by Bede or Gregory of Tours. Though of earlier origin than the tenth century, the first written records of it are in a German sermon of the twelfth or thirteenth century and in the Legenda Aurea of the end of the thirteenth century Caxton has rendered it thus:

‘And because the mortality ceased not, he ordained a procession, in which he did do bear an image of our Lady, which, as is said, St. Luke the Evangelist made, which was a good painter, he had carved it and painted it after the likeness of the glorious Virgin Mary. And anon the mortality ceased, and the air became pure and clear, and about the image was heard a voice of angels that sung this Anthem:

Regina Coeli laetare! Alleluia. Quia quem meruisti portare: Alleluia. Resurrexit sicut dixit: Alleluia.

and St. Gregory put thereto

Ora pro nobis, deum rogamus: Alleluia.

At the same time St. Gregory saw an angel upon a castle, which made clean a sword all bloody, and put it into the sheath, and thereby St. Gregory understood that the pestilence of this mortality was passed, and after that it was called the Castle Angel.’