The story behind the work is that Mycenaean King Agamemnon offended the goddess Artemis. She retaliated by stopping the winds in the Athenian harbor and stranding the Greek navy on its way to fight at Troy. To appease Artemis and allow the navy to sail, Agamemnon was ordered to sacrifice his daughter, Iphigenia. The painting captures the moment when the girl and her mother, Clytemnestra, realize the horrible truth. Agamemnon enters the room with a band of men to seize Iphigenia, who, with a terrified sister, clings to her mother.
SOURCE: NASHER MUSEUM OF ART