It is said that this is the one movie Bergman made that he was so disappointed with that he does not want it to be shown, and because he is so highly respected it's been screened very few times. Neither has it been released on VHS/DVD.
The name of the leading villain in this spy movie, Atkä Natas, is an anagram for "Äkta Satan" (Real Satan) in Swedish.
The name of the Liquidatzian boat, "Mrofnimok Gadyn", read backwards is "Kominform Nydag". Ny Dag New Day is the Swedish Communist newspaper.