Based on a section of Lillian Hellman's series of portraits 'Pentimento' (1973), though the 'Julia' in question is believed to have been a fictionalized account of the life of Muriel Gardiner, who did work in the Resistance in Austria but returned to the US in 1939. You've got to watch these writers, they're always making things up.
(We know Hellman of course from The Little Foxes and also Watch on the Rhine, though have yet to catch either version of the Children's Hour, the first of which, filmed in 1936 by William Wyler, apparently the best, though he directed the 1961 version also. Ah. I now see that we do have the later version and watched it last in 2005.)
Anyway, Alvin Sargent's screenplay is about two girl friends from teenage years. Julia is brought up in a rich family, grows to hate privilege and becomes a socialist, friend Lillian becomes a writer, involved with Dashiell Hammett. They haven't seen each other for years when Lillian is summoned to Vienna and finds her friend severely battered. She loses touch, but then (I'm not quite sure what year this is, but the film begins in 1934) is asked to help her on a mission to Berlin - and it's this section of the film that is most exciting in almost a Hitchcocky way, as Lillian is watched and helped and spied upon on her trip from Paris to Berlin to Moscow.
The cast is good: Jane Fonda, Vanessa Redgrave, Jason Robards, Maximillian Schell, Hal Holbrook, Rosemary Murphy, Meryl Streep, and Dora Doll and Elizabeth Mortensen as her two fellow passengers on the train. Redgrave, Robards and Sargent won Oscars; BAFTA awarded Fonda, interestingly enough, the Film and Sargent, as well as bestowing Douglas Slocombe his third BAFTA. Naturally his buddies Chic Waterson and Robin Vidgeon are part of the crew, though the camera movement is infrequent, with use of subtle zoom here and there. Generally Zinnemann has chosen to film the performers too much in close up. It's an artful piece of work, though, and editor Walter Murch mixes things up wonderfully well.
Zinnemann was of course one of Wilder's Berlin buddies on People on Sunday - quickly moved to the US, Austrian by birth.
It's quite a harrowing story, really, almost European in its treatment. Really good and well overdue.