Torn Curtain (1966) – IMDb

Torn Curtain: Directed by Alfred Hitchcock. With Paul Newman, Julie Andrews, Lila Kedrova, Hansjörg Felmy. An American scientist publicly defects to East Germany as part of a cloak and dagger mission to find the solution for a formula resin before planning an escape back to the West.

https://www.imdb.com/title/tt0061107/