This scene tells the story of the murder of Saint Peter Martyr, a friar of the Dominican Order who was killed by members of the Cathars, a heretical sect whose teachings he had spoken against publicly. The saint is shown on the left – he has collapsed to his knees, an axe lodged in his skull. His killer makes a final blow to his chest with a dagger.

Until recent cleaning and restoration the picture was covered by layers of varnish which had darkened over time, as well as old repainting. The cleaning revealed the cleaver in the saint’s head, a characteristic feature of images of him. Cleaning also revealed that the dark tree trunks are interspersed with glimmers of bright summer light. This light is perhaps a promise of salvation – Peter’s life and his martyrdom for his faith led to him being declared a saint in 1253.