I, Claudius - Season 1 Episode 8

Sejanus divorces his wife in order to marry Livilla but Tiberius refuses permission and suggests that he marries Livilla's daughter Helen instead, which so enrages Livilla that she poisons Helen. With Tiberius spending most of his time on Capri Sejanus seems to hold absolute power in Rome and, to consolidate his position, has Agrippina and her son Nero banished and her other son Drusus arrested and sent to prison where he dies. A shocked Antonia finally sees evidence of the plots her daughter Livilla and Sejanus have hatched together and has Claudius smuggle the incriminating facts to Tiberius. As a result the new prefect of the Praetorian guard Macro kills Sejanus and his followers are also put to death.