First, a word about the format - I don't know whether this was a movie or a TV series, b/c I saw it aired in pieces on PBS back in the 1980s. I don't even recall if it was originally voiced in english, dubbed over, or subtitled. I'll just call it a movie for now.
The movie seemed to be set in Europe in what looked like the 1960's or 70's, where almost all the people were gone. The protagonist was probably a 20-something man, who routinely visited a psychiatrist. I think the protagonist also had a girlfriend, but most of the dialogs seemed to be between the man and the doctor.
It was kind of a mystery where all the people had gone, and I think the man was nominally seeing the doctor to cope with the stress of it all, or had amnesia and suspected he knew The Truth. However, it turns out that the doctor discovers that the man is somehow the key to the reality that the characters share, and during hypnosis sessions, discovers he can manipulate the man and thereby reality. To make it easier for himself, the doctor gives the man a code word to return the man to a hypnotic trance on command. The code word, I am positive, was 'Antwerp'.
I don't think I ever saw the end of this, but the 'truth' might have been that World War III was fought with neutron bombs, and that the man was actually just dreaming everything as he wandered around the city, dying. Or not. It would be nice to know how it turned out, but I don't even have the name of the show.