The main plot of Horrible Histories Ruthless Romans follows the struggle of young Rassimus to achieve glory as a gladiator and obtain his freedom. Rassimus, a slave and an ambitious gladiator-in-training, has been raised as a foundling by the great gladiator trainer Lucius Gladius, and spent nearly 12 years in his service. Lucius has now given him a chance to begin his training, and Rassimus hopes that he will be successful and one day become a citizen of Rome.