Stanwyck and Menjou are on top form here, a real pleasure to watch, and the camera-work is exquisite; the story/pacing is weak in places but you won't mind this much (perhaps hardly notice) unless you're immune to the former. The film depicts, over a period of about 20 years, a complex clandestine love-relationship between the two leads, leaving some space for individual interpretation - not at all like most films made under the appalling thirty year tyranny of the Hayes code introduced a couple of years later. Forbidden is a serious, thought-provoking and often very moving film, with careful, 'arty' composition and psychologically-loaded lingering shots, but it also contains moments of melodrama (not in bad way) and humour (laugh-out-loud but quirky, not slapstick). Highly recommended, along with Capra/Stanwyck's The Bitter Tea of General Yen, made the following year. I give it a 7 - reluctantly, in my effort to be objective with regards to the story. I watched it on the big screen and I 'felt' it as an 8.
