Released theatrically in Europe, Cosa Nostra, Arch Enemy of the FBI originated as "The Executioner", a two-part episode of the weekly TV series
The FBI. The series' usual stars Efrem Zimbalist Jr.,
Philip Abbott and Stephen Brooks are joined on this occasion by guest artists
Walter Pidgeon,
Celeste Holm,
Telly Savalas and
Susan Strasberg-and, way down on the cast list,
Robert Duvall. The story concerns double-crosses within the inner circles of La Cosa Nostra. The story concludes as mob boss Pidgeon orders the death of witness Holm-with the victim's nephew Savalas as the hit man! "The Executioner" first aired on two consecutive Sundays: March 12 and 19, 1967. ~ Hal Erickson, All Movie Guide