For two years the Roman general Marcellus besieged Syracuse, and for two years the city's greatest mind, Archimedes, held him off with giant claws that lifted ships out of the water and catapults that never seemed to miss. Now, during a festival, the Romans have slipped over the walls. Archimedes, seventy-five, is drawing circles in the sand, working on a problem. Ancient writers say Marcellus had ordered him spared. We leave before anyone arrives. The words are imagined.