The dark background contrasts strongly with the pale face of Saint Peter who, as recounted in the New Testament, denied Christ. This contrast assumes a symbolic intensity: darkness dominates, but the saint’s tearful eyes look upward, seeking light and forgiveness. The chiaroscuro—or tenebrism—is typical of Caravaggio’s influence on 17th-century Spanish painters and enables the viewer to focus on certain highly realistic details, as here in the craftsmen’s marked hands.
At the bottom on the right, a stone, worn book, and key can be made out. These attributes confirm the saint’s identity: the keys of Heaven and the stone referring to the words of the gospels in which Christ declares, “You are Peter and upon this rock I shall build my church.”