Alain Robbe-Grillet (the writer-director of this movie) casts himself as a film-maker who, along with the script girl at his side, plot out a "thriller" involving a drug courier. I will emphasize putting 'thriller' in quotation marks, because I found nothing thrilling about "Trans-Europ-Express". They did hook me though, briefly, during the hilarious first 15 minutes. The plot of the movie-within-a-movie was taking shape while the filmmakers commented on it.
Sample dialogue: "Is this really how a drug courier works?"
"Well, yes, because this is how the character is doing it."
A great setup with all sorts of opportunities. Unfortunately, I have to regard this movie as opportunities wasted.
The actual "movie" - about the drug courier - is flaccid, amateurish, and un-involving. But since the film is more about commenting on this type of movie than about the movie itself, its shortcomings could be forgiven. However, the running commentary isn't utilized enough to make that aspect interesting, and the actual "movie" was, for me, just not engaging.
This might have been a wonderful mystery/thriller/crime-drama but it didn't know how to be that. It might also have been a fantastic comedy, but the movie doesn't do enough with the premise after its wonderful and hilarious opening minutes.
I don't know what the first meta-film was - Had any movie before it attempted what this one was after? - so I will credit this for its originality. I can't recommend it otherwise. You should probably watch Truffaut's "Shoot the Piano Player" instead.