Cassius and Titinius watch the battle from another part of the field.
When Cassius's standard-bearer (the guy who carries his battle flag) tried to run away, Cassius killed him and took up the flag himself. This guy is merciless!
Titinius doesn't comment on this behavior but points out that Brutus came down on Octavius's army too early. Though they were initially weaker, Octavius's men now appear to be overtaking Brutus's, and Antony is enclosing Cassius's. The situation is looking pretty dire for Cassius and Brutus.
Pindarus comes to Cassius and Titinius with the news that Antony has invaded Cassius's tents. He tries to get Cassius to run away, but Cassius is distracted by a set of troops in the distance.
Cassius sends Titinius off on horseback to see whether the troops are friends or enemies. He also sends Pindarus higher up the hill to watch and report on Titinius's progress.
Cassius notes to himself that his birthday is a good day to die, his life having come full circle.
Cassius is resigned to his fate, but he still fights on. Pindarus reports on Titinius play by play. A horde of horsemen has surrounded Titinius. Now they've overtaken him. And now they're shouting with joy. It looks like the worst has happened.
Cassius calls for Pindarus to stop watching. He laments that he's such a coward to have sent his best friend Titinius to his death. Pindarus returns to Cassius's side, and Cassius speaks to him.
Cassius reminds Pindarus how he took him prisoner at Parthia and spared his life on the condition that he do whatever Cassius asked him to. Cassius then tells Pindarus how to make himself a free man: he should kill him with the very blade he used to kill Caesar.
Pindarus stabs Cassius, who dies declaring that Caesar is avenged by the same sword that killed him.
Pindarus, now hovering around Cassius's body, claims that this wasn't the way he wanted to gain his freedom, and that if he had his own will (and hadn't been Cassius's servant), he wouldn't have done it. He declares that he'll run far away so no Roman will ever see (or enslave) him again.
Messala then enters the scene with Titinius (who – surprise! – is not dead), announcing the new state of the battle: they're basically even on both sides. Brutus has overtaken Octavius's forces, while Antony's forces have beaten Cassius's men.
The men are stoked to tell Cassius that all isn't lost, but then they see his dead body, which is in no condition to accept good news.
Titinius realizes that Cassius must have misunderstood what had happened on the hilltop.
Messala is more Action Jackson than super-sleuth; he goes off unhappily to inform Brutus of Cassius's death. Meanwhile, Titinius is left to find Pindarus.
It doesn't matter where Pindarus is, and Titinius doesn't even look for him. Instead, Titinius explains what actually happened in the scene that Cassius killed himself over. Titinius was indeed overtaken, but by friends of Brutus and Cassius on horseback. The shouts Pindarus heard were shouts of joy for Cassius's side. They overtook Titinius to put a wreath of victory on his head, which Brutus then wanted the rider to give to Cassius.
Titinius still has the doomed crown, which, in a dramatic moment, he places on dead Cassius's head.
Titinius then cries, "By your leave, gods! – this is a Roman's part," and proceeds to stab himself with Cassius's sword. Titinius dies beside his friend.
Messala and Brutus arrive just in time to find that Titinius has played Ultimate Mourning and killed himself.
Brutus cries out, "Julius Caesar, thou art mighty yet!" (He might be suggesting that the ghost is out convincing people to kill themselves, or he might be talking about his effect on the conspirators' consciences.)
Brutus laments that two of Rome's bravest men should lie here this way. He prophetically calls Cassius "the last of all the Romans," meaning the last of the old school Romans that prefer death to subjugation. Brutus says he knows he ought to cry over Cassius, but now is not the time for crying.
In the meantime, they decide not to hold the funerals in the camp, as funerals are no way to boost troop morale. Still, it's only 3 o'clock, which means there's time to try their luck against the enemy again, in the hopes something might be accomplished before dinnertime. Brutus gathers his remaining friends for the fight.