The battle goes badly for Cassius's troops. Cassius angrily reports that his own soldiers have run from the enemy. Brutus appears to be having some success, but his soldiers have fallen to looting.
Pindarus tells Cassius to flee because Antony's troops are upon them. Cassius refuses. He sends Titinius to investigate whether there really are enemy soldiers at their tents, as Pindarus told him. He sends Pindarus higher up the hill to gather information. But Cassius knows in his heart that he is defeated. Pindarus reports that Titinius has been captured. This is the final blow for Cassius, who instructs Pindarus to kill him with his sword, the same sword that killed Caesar. Cassius dies.
Titanius and Messala enter, reporting that Brutus has triumphed over Octavius even as Cassius's army has fallen to Antony. They discover the dead Cassius. Titanius laments that Cassius killed himself because he misunderstood the situation. Titanius had in fact been welcomed and treated like a friend; he had not been captured at all. Filled with grief, he kills himself.
Brutus enters with Messala, who has brought him the news of Cassius's death. Brutus exclaims that Caesar is mighty yet, and it is his spirit that has caused their defeat. He laments the death of two great Romans, and then tells his generals to prepare for another round of battle.
This scene is a good illustration of what is sometimes called the "fog of war." Reliable information is hard to come by, and Cassius dies because of it.