After the death of Octavian, the rebel populations of Illyria and Pannonia pose a grave threat to the Roman Empire. Tribune Marcus Ventidius is sent to subdue the uprising and, after a bitter battle, captures Pannonian chief Magdus together with a number of women hostages. These include Magdus's own daughter Helen, betrothed to cruel Illyrian warrior Batone who has killed many Romans. Julia, daughter of the Roman governor Messala, is in love with Tribune Marcus and, jealous of his sympathy for the barbarian girl, plots an escape by Helen and her father. Pursuing the fugitives, Marcus crosses a mountain pass where Batone has laid a trap.