While other directors were still trying to get the hang of audio production, DeMille added sound to spectacle seamlessly, meanwhile pulling himself out of a personal slump, and all on a budget. Based on a 1895 play by English actor Wilson Barrett, and filmed once or twice already, Sign of the Cross was not a life of Christ in the manner of King of Kings, but rather a sequel to the Gospel story, along the lines of Quo Vadis: Christ against Empire, that is, Christians against Rome, in a titanic struggle that once again found its way into the Coliseum.

"Roman Boy Meets Christian Girl" was always the dramatic and romantic center of such films, and here an Imperial Prefect named Marcus Superbus falls for a pretty believer named Mercia, just as the Emperor has decided to crack down on the Christians. Marcus's rival, Tigellinus and spurrned lover, Nero's wife, Poppaea, seek to use this weakness to each settle their own personal scores with the Prefect. Meanwhile, this palace intrigue is intercut with sequences involving the underground Christians: their secret knocks, secret signs (including that of the Cross, of course), and secret meetings. The two worlds collide, violently and in scenes like the notorious "Naked Moon" sequence, when a captured Mercia is made sport of by orgy revelers, including the seductive Ancara, whose impassioned song and dance is interrupted by hymn-singing Christians on their way to the arena. Thus is provoked a heated and inspiring song duel, reminiscent of Die Fatherland versus La Marseillaise at Rick's Café. The conflict ultimately climaxes in the arena, and especially underneath, in the fervent and classic last-minute arguments for and against martyrdom.

A coliseum sequence is always splendid spectacle, and this one rivals anything done since in wide screen and with CGI. DeMille cranes down from the heights to ground floor, listening to conversations along the way. A couple shots later, the camera lowers to the basement and through the window grate, to Christians preparing themselves for their impending doom. There's also a terrific shot sequence inside the Coliseum: starting high looking down on gladiators entering, we crane down to look up at Caesar as the gladiators pass through the frame, then pull in close on Caesar, cutting to his POV of gladiators saluting below. The rhythm shifts to cutting: between the action on the field and in the stands. We see various kinds of spectators, watching, wagering, reading programs, a pair of lovers who ignore the games to gaze at each other, a victim's mother quietly sobbing. It almost seems the movie audience is being implicated in the gory bloodlust, but clearly DeMille takes so much pleasure in it himself one can't imagine him caring to press that point too hard. A menagerie of beasts is set loose on the victims — elephants, tigers, crocodiles, bulls; midgets fight Amazon women; armed men fight each other. It's a three-ring circus, affirming the kinship between the director and the showman he most resembles, P. T. Barnum, whose own story would be given the DeMille treatment many years later. Typically, DeMille takes just as much care with the martyrs as they wait their turns, comforting each other, praying the Lord's Prayer together, and climbing that fateful stairway to the arena.

However, that "pinch of incense" offered to Christian sensibilities proved inadequate to cover the excesses. Religious people made a fuss over the "Naked Moon" sequence, a few nearly-naked martyrs, and that most infamous of DeMille's bathtub scenes, Claudette Colbert's repose in a luxuriant tub full of milk. Despite the director's high-toned moralizing, his lip service to the Production Code and disparagement of other director's gratuitous sex scenes, DeMille was probably one of the main reasons the Code was finally given teeth. The renewed enforcement of moral censorship starting in 1934 effectively put an end to the genre of ancient spectacles for more than a decade.

(Of course, when a new cycle began, it was launched by none other than DeMille. With Samson and Delilah (1949), in some ways a warm-up for his 1956 magnum opus, The Ten Commandments, DeMille was to provoke a new round of ancient spectacles and Biblical Epics just in time for the introduction of color film and widescreen projection formats.)