With Tiberius retired to Capri, Sejanus plans to tighten his grip on Rome and divorces his wife so he can marry Livilla. But he also has powerful enemies and his attempts to consolidate power set in motion a bloody chain of events.

Claudius has high hopes of a return to a Republic when Caligula insanely proclaims himself a god and his sister a goddess... but Rome officially accepts his divinity.

Caligula's erratic behaviour continues, as he makes his horse a senator and turns the palace into a brothel. Many in the Praetorian Guard grow to realise that their ruler is insane and, fearing the collapse of Rome itself, believe that something needs to be done.

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