Caesar defeated Pompey at the war. Caesar came back and people are celebrating his victory. He was walking through the streets when the Soothsayer yells after Caesar saying "Beware the ides of March!" Caeasar turns around and has him say it again. Then walks back in the direction he came in.
Act IV: Scene ii
The conspiritors, who is run by Cassius, shows up at Brudus's house. Cassius takes him aside and gets him to be a part of the conspiracy. Brudus agrees and says, "Give me your hands all over, one by one." And with that Brudus joins and takes over the conspiracy.
Act V: Scene V
Caesar is killed by the conspirators at the capital. When Caesar sees that Brudus stabbed him he said, "Et tu, Brutè Then fall, Ceasar. Caesar ends up dying in the capital. The conspiritors cheer and proclaim freedom.
Brudus is waiting to start the battle. Cassius comes riding up and says, "Most noble brother, you have done me wrong." Then they end up going back to Brudus's tent to have a fight out of earshot. The fight shows that they can't work together really good.
Brudus realizes that he is going to loss the war and runs up to a hill. He asks 3 people to kill him, but they all said no. Finally his servant Pindarus said yes. Brudus ran towards the sword and killed himself. With his final breath he said, "Farewell good Strato - Ceasar, now be still: I killed not thee with half so good a will."
Arrogance can get you killed. When Caesar tells the Soothsayer that its the ides of March and he isn't dead, he is being arrogant. Caesar says to the Soothsayer, "The ides of March are come." If Caesar was not so arrogant he would have heeded his warnings and maybe had not been killed.