Deutscher and Hackett

Niobe is a powerfully dramatic, unfinished painting ... (that) comes from the best period of his late mythological decorations.

The subject of the picture is taken from Greek mythology, showing the killing of Niobe's sons and daughters by Artemis and Apollo. Niobe was the daughter of Tantalus, the mother of seven sons and seven daughters. She boasted of her superiority to the goddess Leto, who had only two children, Artemis and Apollo, fathered by Zeus, King of the Gods. Artemis and Apollo revenged their mother by slaying with their arrows all of Niobe's children.

(EXTRACT FROM A LETTER WRITTEN BY DAVID THOMAS AUTHENTICATING AND DESCRIBING THE PAINTING)