Il serpente

The convoluted spy movie "Le serpent" ("Night Flight to Moscow" in English) features Yul Brynner as a Soviet colonel who defects to the United States, claiming that he has info about an assassination network. Much of the movie focuses on the intelligence communities in different countries investigating what he said. This probably would have been easier to watch in the cinema, since you need to know when to have subtitles turned on: they suddenly start speaking different languages at random times.

It's not a great movie, but worth seeing. Just understand that this is a complicated one; no James Bond stuff here. Also starring Henry Fonda, Dirk Bogarde, Farley Granger, Philippe Noiret and Virna Lisi.