"Paris, 1789 and the Great Revolution is underway. The noblest heads in the land are being lost to the fearful embrace of Madame Guillotine.
Sir Rodney Ffing (Sid James), an Englishman of the finest breeding, decides to lift a little finger (or even two). Daring rescues are staged and a calling card is always left bearing the contemptuous sign of that damned elusive The Black Fingernail.
Searching for Ffing and his faithful partner, Lord Darcy, are the fiendish Citizen Camembert and Citizen Bidet.
Will the Fingernail's true identity be discovered? Will Camembert and Bidet have the last laugh? Will you manage to stop laughing your head off in this hilarious romp with the best of the Cary On team?"