Skullduggery is a 1970 American adventure film directed by Gordon Douglas produced by Saul David and starring Burt Reynolds, Susan Clark. It is based on the French novel Les Animaux dénaturés (1952) (variously titled in English as You Shall Know Them, Borderline, and The Murder of the Missing Link) by Jean Bruller (writing under the pseudonym "Vercors"). Source: Wikipedia (en)