The beginning of Act IV, Antony, Octavius, and Lepidus are talking about there family members that must be killed. They are doing this for the Good of Rome and for power.
Long Live! hail, Caesar!
Towards the middle of Act IV, during the long conservation about what they plan and are willing to do, Brutus tells Cassius that Portia has died. She killed herself by swallowing fire because of Brutus and his absence away from her.
At the near end of Act IV Brutus had Lucius plays some nice calming music to sleep when Brutus hear the Ghost of Caesar talking to him. The ghost tells him to see him at Philippi and the disappears and Brutus says he will.
Beginning of Act V, Antony, Octavius and there army meet in the middle of the plains of Philippi to Brutus,Cassius and there army. They talk in battle terms and Antony and Octavius will avenge Ceasar.
Middle of Act V, Cassius is with Pindarus and sees that Titinius has been captured and they are losing the battle. Cassius tells Pindarus to stab him for revenge of Caesar and Cassius dies and Pindarus runs of for freedom. Titinius find Cassius dead and then explains that he cannot live without him and then kills himself to be with Cassius and he does.
End of Act V, Brutus now knows the battle is lost and Cassius is dead he then tries to convince his men to kill him and which Strato does and Brutus runs into the Sword killing him. Before he did he said goodbye to Strato and "Caesar, now be still.