Nick Carter had undergone some changes since its creation :first a sleuth a la Sherlock Holmes ,he went pulp fiction in the thirties;then ,in the wake of James Bond,he became a secret agent.Indeed,"Le Trefle Rouge" is a poor man's "Thunderball":rockets were stolen and these dangerous weapons may put the world in jeopardy.Played by Eddie Constantine,who is not exactly the original hero,this Nick Carter is the hero of a story completely devoid of interest.
In one curiously circular and self-referential scene, Constantine as Carter enters a house where he finds a large collection of Nick Carter pulp magazines and other Nick Carter memorabilia.(IMDb)
The main interest is the presence of Jo Dassin,Jules' son -whose career as a singer had just begun and would become big in the late sixties/seventies- ,wearing a mustache :he was wise enough to call it a day,as far as cinema was concerned ,and to concentrate on his buoyant singing career.