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In 542, plague reached Constantinople from Egypt and lasted about four months. Deaths climbed to 5,000 a day, then 10,000 and more. Justinian sent the official Theodorus with imperial money to pay for burials, but once every grave in and around the city was full, workers tore the roofs off the fortification towers at Sycae, across the Golden Horn, and filled them with corpses until a stench spread over the city.
In a mass-casualty event, the normal systems for handling the dead fail in order: private burial first, then state-funded graves, then any structure that can hold bodies. Each step trades dignity and hygiene for throughput. The point where a society starts repurposing its defensive infrastructure is a readable measure of how completely its routine capacity has collapsed.
Procopius reports that during the plague even notoriously dissolute people turned to piety and upright conduct. They did so out of immediate terror of death, not changed conviction. As soon as the disease receded and they felt safe, most returned to their old behavior or worse, which shows that virtue coerced by acute threat does not persist.
He notes the buboes, the coma or delirium, and that physicians' prognoses repeatedly failed. He also notes that those who nursed the sick fell ill no more often than others, and that the disease always spread from the coasts inland. Separating firm observation from unsupported explanation keeps the record useful even when understanding is absent.