Claudius is happily married, while the mad Caligula has been assassinated. To his astonishment, Claudius has been proclaimed emperor by the Praetorian Guard.

Claudius has ruled wisely for a year with the support of Messalina, whom he deeply loves. Convinced of her devotion, he is totally unaware that she is deceiving him.

Almost at the end of his family history, Claudius' thoughts turn to the future of Rome.