The Tribunal of the Holy Office of the Inquisition was established in 1480 by Catholic Monarchs to maintain Catholic orthodoxy in their kingdoms and to replace the Medieval Inquisition which was under Papal control. The Inquisition was originally intended to ensure the orthodoxy of those who converted from Judaism and Islam but, eventually, it assumed that responsibility for the whole population.
This scene represents an auto-da-fe, presided over by Saint Dominic, in which some Albigensian heretics are being judged. Some of the accused are already being burned, while two others, in the foreground, await their turn. They are wearing the Sambenito (a cloak worn by those condemned by the Inquisition). In the background, yet others await the judgment of Saint Dominic.