This painting is of Medusa taking revenge on a man by turning him to stone. It was inspired by the Mandelbaum translation of The Metamorphoses of Ovid:

"Medusa was astonishingly fair; she was desired and contended for - so many jealous suitors hoped to win her. Her form was graced by many splendors, yet there was no other beauty she possessed that cold surpass the splendor of her hair - and this I learned from one who said he'd seen her. Her beauty led the Ruler of the Sea To rape her in Minerva's sanctuary (so goes the tale). Jove's daughter turned aside chaste eyes: the goddess hid her face behind her aegis - but she made Medusa pay: she changed that Gorgon's hair to horrid snakes. And to this day, Minerva, to dismay and terrify her foes, wears on her breast the very snakes that she herself had set - as punishment - upon Medusa's head."