Paris, 1803: as Napoleon is set to declare himself as leader of the freshly instituted French Empire, an underground movement of Royalist rebels is fired up by the daring deeds of the mysterious Purple Mask. The unknown swordsman boldly rescues noblemen from the guillotine and kidnaps Napoleon’s cronies to extort ransom money for the Royalist cause.
Laurette de Latour (Colleen Miller), the niece of a jailed marquis, hatches a scheme in which the foppish Count Rene de Traviere (Tony Curtis) imitates the Purple Mask and allows himself to be captured to encourage the release of her uncle. Little does Laurette realise she has engaged the Purple Mask himself!
Continuing the charade, and attracting amused ridicule, Rene is swiftly imprisoned alongside the marquis. But the intrepid one has a trick or two up his lacey sleeve, and as the two men are marched towards the guillotine, at an agreed signal rebels spring from the Paris sewers, swords at the ready.