Portia, Brutus' wife, is a mess. She tells Lucius, the servant, to run to the Capitol, then yells at him for not leaving, even though she hasn't yet given him any instruction on what to do when he gets there.
Portia is worried, but she doesn't even know what Lucius should look for. Brutus didn't look well when he left the house that morning, and she decides Lucius should look after her husband and see what Caesar is up to and whom he's surrounded by. Though she hasn't heard the murder plan directly from Brutus' mouth, it's clear she suspects something awful.
Portia then starts with a fright, thinking she has heard a noise, though Lucius claims he's heard nothing.
A soothsayer (they pop up a lot in ancient Rome) arrives at Brutus' house to tell Portia that Caesar hasn't come to the Capitol yet. The soothsayer hopes to meet him on the way there, with an offer to befriend him.
Portia worries about this and asks whether something is being plotted against Caesar – why does he need more friends? The soothsayer says he hasn't heard of anything, but he fears something will happen.
The soothsayer heads off in hopes of finding a place to speak with Caesar himself and not be crushed by the crowd.
Portia grows even more faint. She asks that heaven speed Brutus in his "enterprise." Worrying that Lucius has overheard her, she covers herself with a paltry lie, pretending that the "enterprise" is some small request Brutus has made that Caesar won't grant. She does know something, and she's not saying what.
Finally Portia tells Lucius to tell Brutus that she's "merry," and that she'd like Lucius to bring back news of Brutus. She clearly isn't merry, dear reader, and seems to suspect the worst.