One would dearly love to play Devil's advocate and say something positive about this lamentable opus but it has alas no redeeming features whatsoever and is nothing more or less than a stinker.
For an actor of Robert Ryan's magnitude it represents the bottom of the barrel but at least he has a few decent roles still to come. As for Stewart Granger this is sadly typical of the mostly mediocre material of his post MGM career. Nadia Gray, Marius Goring and George Coulouris make up the numbers whilst one is able to put a face to the voice of King of the Dubbers, Robert Rietty, as a policeman.
The editing is simply atrocious and the whole enterprise is utterly devoid of momentum. Although director Don Chaffey is no doubt known to devotees of the Fantasy genre, he ended up where he belonged, in Television.