The File on Devlin (1969)

A young woman finds herself engulfed in Cold War intrigue when her father, a Nobel Prize-winning author, vanishes while travelling near the Russian border. Entrusted by her father with an unfinished book he was working on before his trip, the young woman becomes engaged in a power struggle over the material with her estranged stepmother. Suspiciously befriended by a journalist in the midst of the crisis, the young woman ultimately learns that no one is to be trusted - as her father's work is of interest to the intelligence departments of several countries.