The Doctor and Peri discover that Rome has advanced far beyond its natural means, and they must recruit the aid of Ptolemy Caesar to prevent his half-siblings, Cleopatra Selene and Alexander, from waging a potentially world-ending war with each other.
Later literary accounts often attributed Pompey's murder solely to Septimius, as in the poem Pharsalia by the Roman poet Lucan, or in modern fictionalizations such as the George Bernard Shaw play Caesar and Cleopatra, and the HBO television series Rome (depicted in the episodes "Pharsalus" and "Caesarion").