The Sicarii were a group of Jewish zealots and assassins who opposed Roman rule in the years before the destruction of Jerusalem. They were known for the small daggers, sicae, which they carried under their cloaks and used to quickly assassinate Romans. The culprits would then disappear into a crowd. The term 'cloak and dagger' comes from their actions.
James Dean was offered the role of Basil, the sculptor, but he and his agent thought the script was poor. Paul Newman took the role, and later regretted it. Newman was in the running for the role of Cal Trask in East of Eden (1955), which was eventually played by Dean, and made him a star. While shooting East of Eden (1955), Dean went over to visit Newman on the set of this film, and met the love of his short life, Pier Angeli.
Despite this film's failure at the box office, it won Paul Newman the Golden Globe as Most Promising Male Newcomer of 1954, a rare instance of Globe voters ignoring popular opinion and giving a statuette that would later prove prescient.
The background designs in this film were unusually minimal and abstract for the era. Most biblical sword and sandal extravaganza productions had suitably opulent sets and costumes.