 The movie differs in many respects from the novel; it is set in the modern day (using the 1986 flyby of Halley's Comet as a plot element), and the character of Carlsen (an American colonel named Tom) is much weaker, with a more obsessive relationship to the female vampire.The character of Colonel Caine of the SAS is given a much more prominent place, and the story's vampirism is more evocative of traditional vampire legends in its details, most specifically in how the vampires can be killed (a leaded iron shaft through the "energy centre two inches below the heart", a possible allusion to Eastern-mysticism chakras) and in the process by which vampire victims become vampires themselves, a much deadlier and more prolific contagion in the film.Robert G. Allen

Robert Gray Allen (August 24, 1902 – August 19, 1963) was an American businessman and a Democratic member of the U.S. House of Representatives from Pennsylvania.