Neocle enters the catacombs, mastering his fear. He joins the Greeks who are preparing to make a final stand. In the distance, Pamira and the Greek women are heard in prayer. Cleomene recognizes Pamira's voice; but, feeling betrayed by her, he swears she is no longer his daughter. Maometto approaches and once again offers to marry Pamira and make peace with the Greeks. Cleomene would rather see Pamira die than married to their enemy. Neocle returns and reveals to Maometto that he isn't Pamira's brother, he's the man her father wants her to marry. Maometto, enraged, departs for the field of battle.
