One effect of watching this one is that you will always read Frost's "Stopping By Woods" from a very different point of view.
No question, there's a whole lot of good acting in Don Siegel's "Telefon" (from Tyne Daly, for instance), but the story, from Walter Wager's novel, is, at least partly, ridiculous. Criticism of international secret policy comes off o.k., claiming that what intelligence agencies have always lacked most is intelligence. But it's more about suspense and action; especially the blowing up of a whole valley is staged with Siegel's dynamic perfection routine.
The film has got Charles Bronson in its center and he does his usual fine job as an ultra-cool Soviet major smuggled into the U.S. in order to exterminate a fellow KGB agent (Donald Pleasence) who has gone crazy there and is now endangering the whole Cold War balance system.
Please note the important rôle telephones play throughout the whole film, not just for Pleasence's ambitions. And watch out for Roy Jenson as his last victim, a man who has played lots of minor parts in major movies. - And don't forget listen to the film, as Lalo Schifrin's score is very fascinating once again.