As the conspirators plan Caesar's murder in Act 2, they voice the concern that Caesar might decide against going to the capital--in which case the conspirators will be unable to carry our the murder. Decius, recognizing that Caesar can be flattered rather easily, volunteers to visit Caesar at home and convince him to go to the capital. Though Caesar does initially decide not to leave his house (Calpurnia initially convinces him that something bad might happen), he changes his mind when Decius suggests that the Romans might view him as a coward if he doesn't go to the capital. Caesar agrees, and leaves with Decius.
In 3.1, The conspirators gather near Caesar and approach him under the pretense that they wish to have Publius Cimber pardoned. When Caesar asks "What is now amiss/That Caesar and his Senate must redress," Metellus Cimber requests that his banished brother, Publius, be given permission to return to Rome. Pretending to support Metellus's petition, Brutus and Cassius kneel beside Caesar and also plead on Publius's behalf. Though the conspirators' pleas seem sincere to Caesar, they are just excuses for the conspirators to get close enough to Caesar to murder him.