One day a woman accuses Piazza of being an untore (literally, a greaser): a spreader of disease by anointing walls and furnitures with a pestiferous ointment.

According to a superstitious belief held by the people, these untori were in league with the Devil, and were responsible for the spread of the pestilence.

Immediately the Church and the Inquisition scapegoat the two artisans for the outbreak, and subject them to trial by torture, despite the protests of Cardinal Borromeo.

Innocent victims of a panic which has gripped the populace, Piazza and Mora are found guilty of the imaginary crime of smearing poisonous substances about in the city to induce plague.

Afterwards, a pillar (The Infamous Column of the title) is erected in the square which beheld their execution, with a warning for the masses, to guard against eruptions of public hysteria ever again.