Le système du docteur Terrier

On their honeymoon in the north at Annette's godfather's, two counterfeiters blackmail Vidocq: either he helps them kill the English messenger with whom they're going to exchange counterfeit English bills for counterfeit French ones, or they denounce him. What's more, Flambart is in the area and Annette's godfather, who believes Vidocq is being pursued as a royalist conspirator, must not learn the truth...