In his twenties Caelius became associated with Crassus and Cicero, while he was also briefly connected to Catiline and his conspiracy. Caelius first achieved fame through his successful prosecution in 59 BC of Gaius Antonius Hybrida for corruption. Antonius Hybrida had served as consul with Cicero for the year 63 BC, and his prosecution was a sign of the negative political atmosphere towards Cicero at the time. A year later, in 58 BC, Cicero was exiled, through the efforts of his political enemy Publius Clodius Pulcher. Cicero was recalled from exile in 57 BC with the help of his ally Titus Annius Milo, who was tribune at the time.