Marcellus Gallio, son of an important Roman senator and himself a military tribune, introduces through flashback narration, the might and scope of the Roman empire. Marcellus is notoriously known as a ladies' man, but is captivated by the reappearance of his childhood sweetheart, Diana, ward of the Emperor Tiberius. Diana is unofficially pledged in marriage to Tiberius's regent, Caligula.
In a slave market Marcellus bids against Caligula for a defiant Greek slave, Demetrius and wins. Angrily, Caligula issues orders for Marcellus to receive a military transfer to Jerusalem in Palestine .