This shows the dramatic scene in which Apollo and his sister Artemis (Diana) shoot down the children of Niobe, all those beautiful boys and girls that Niobe had boasted about. You can read the entire story in Ovid's Metamorphoses, Book 6.
You can also find more myths and legends for the week of September 30 - October 6 here. For more information and links to the actual javascript code, see the Myths & Legends Widget Reference Page.