The film's closing credits state that this production was: "Made on location in England and Tunisia and at Twickenham Film Studios - London and at Rizzoli Palatino - Rome. An Italian-British Co-production; Embassy Production; Aston Films Ltd."
The film was released with two endings. The European general release version of the film features an open ending, with Kirk Douglas in exile with his newborn child, and his adult son now successfully developing the plant intended to cause Armageddon. In the shortened version released in U.S. theaters, home video, and network television, a new ending was added where Douglas returns to the company and enters a board meeting having explosives hidden on him. In the final scene, Angel's face is overlaid with an image of an explosion, showing that Robert has successfully thwarted the apocalypse. The U.S. DVD from Lionsgate retains the original darker ending and the Blu-ray from Scream Factory contains both the European and American versions of the film.
This British-Italian co-production was produced by Edmondo Amati for The Rank Organisation and Titanus, and is widely-considered a cash-in on the success of the similarly-themed The Omen, which was released a year earlier. It received mixed reviews, but has become a cult classic.[2][3]