The ancient Roman hero Mucius Scaevola thrusts his hand into the open flames and holds it there as the man he tried to assassinate stands over him, observing along with two guards. The artist showed the dramatic climax of an ancient tale: the Etruscan ruler Lars Porsenna condemned Scaevola to be burned at the stake for attempting to murder him while he besieged the city of Rome. The Roman's bravery so impressed Porsenna, however, that he set Scaevola free.
The design is crammed with fanciful details, all intended as a model for a stained-glass window, one of a series on Roman heroes and heroines. The background shows the towers of Rome, which resembles a walled Renaissance town more than an ancient, classical city, surrounded by medieval siege engines. A heavily ornamented arch supported by a pair of robust columns frames the scene. Profiles of a king and an emperor decorate the coffered arch, while other vaguely classical motifs fill the arch, the sides of the columns, and the frieze along the base. The shield at the bottom remains empty except for the Roman numeral xxiii, perhaps signifying the twenty-third window in the series. The rest of the space could have been filled with further inscriptions.