None But the Lonely Heart stars Cary Grant as Ernie Mott, a drifter who reluctantly returns home to help his sick mother (Ethel Barrymore) run her shop. He has a relationship with Aggie (Jane Wyatt), the understanding girl across the road who takes him as he is, but he's also drawn to Ada (June Duprez). However, her ex-husband, Jim Mordinoy (George Coulouris), doesn't much like their relationship and when Ernie starts working for him it spells trouble.
Apparently, the novel this was based on focused on a much younger protagonist but, I suppose, the studio wanted a vehicle for Cary Grant and shoehorned him into a role that he really doesn't fit. The only scenes that do sparkle are those between Grant and Barrymore, though Grant still looks out of place. Barrymore, for her part, is excellent in an understated performance befitting the ill mother worried about what she's leaving her son with. Jane Wyatt is reasonable as Aggie, though she struggles with some bad dialogue, but June Duprez doesn't impress as Ada. Perhaps it's the character that's too wispy but she certainly doesn't come across as the type of girl the cynical Ernie would fall in love with. Their relationship is integral to the finale but, really, it feels superfluous for most of the film.
The whole thing lacks a direction. For the first half an hour, there's not much at stake, it's all scene setting that could have been done much more quickly. Also, despite the spectre of Ma Mott's impending death, there isn't much for Ernie to lose throughout. There are only a few moments of tension, befitting the small-community feel of the film but meaning it comes across as a bit drab.
Ultimately, None But the Lonely Heart fails on several levels but it does showcase the talent of Ethel Barrymore, and that's never a bad thing.