Brutus is pacing back and forth in his orchard and is talking to hisself saying that Caesar must die because power will take over him and corrupt him
What is the matter my love? I'm sure everything will be alright.
Nothing to worry about love. I'm alright. I will talk to you later.
So what viscous plan do you have now?
Brutus servant brings him a letter accusing him of sleeping while rome is being threatened. He believes that the letter is a protest towards Caesar and thinks the people of Rome are telling him to speak,strike,and redress.
You will see...something that will be best for all of us.
Cassius (walks in) and believes that they should bring Cicero into the conspiracy but Brutus says he wont go for it and Cassius wants to kill Antony but Brutus says that Antony will be harmless once Caesar is dead.
He must die. No ifs and or but's about it.
Brutus wife , Portia, comes into the garden and wants to talk to him to see what has been worrying him. But he doesn't tell her and brushes her off and promises to speak to her later.
Ligarius enters looking sick and confronts Brutus about having a scheming plan. Brutus confirms it and Ligarius becomes happy and walks with Brutus to here more of the plan.
Brutus came to an conclusion that Caesar must be killed. There lies a forged letter but he doesn't question if its real or not and displays a tragic naivete and thinks it speaks to the entire roman population that's there.