Manhãs de Setembro tell the journey of Cassandra, who starts to see things get on track in her life with a place of her own for the first time, a boyfriend who she loves, Ivaldo, a job as a courier in downtown São Paulo, and fulfilling her dream of being a cover artist of Vanusa, a famous Brazilian singer from the 70s. Her life takes an unexpected turn, however, when her ex, Leide, shows up with Gersinho and claims he is Cassandra's son.