Vidocq and the Baroness are in love, but the Baroness suddenly disappears. Fouché assigns Vidocq to protect Napoleon, against whom an assassination attempt is being planned. Vidocq heads north, where Napoleon will fight the decisive battle. Accompanying Vidocq is an emperor look-alike, a champion dagger-thrower who is supposed to distract the assassins. This look-alike, supposedly the victim of a poisoning attempt and then kidnapped, turns out to be the plot to assassinate Napoleon. Vidocq saves the emperor's life, then returns to Paris to discover the identity of the plot's leader...