David Niven takes on the mantle of Baroness Orczy's hero in this classy but a little lightweight take on the escapades of the "Scarlet Pimpernel". Hugely successful at smuggling doomed artisto's from under the nose of the Reign of Terror, the French authorities charge "Chauvelin" (Cyril Cusack) to track down the culprit. He has some leverage with t…