Although the film has all the ingredients of a film noir, like the selfish femme fatale, Bogart, and many night scenes, this is something you could consider a feel-good movie. It pretty much surprised me with its turns and twists and I also wasn't prepared in the least to see Bogart as the sidekick, instead of the lead.
In terms of interesting characters, Ida Lupino as the selfish wife that tries to seduce George Raft's Joe she is definitively at the most intense when she slowly sheds all the layers of sanity towards the end. Although her motives are a bit unclear - the amazing thing about her behavior is that she values love over money. In that perspective the movie feels like a tragedy, as (except for the loan shark) everybody has comparatively sophisticated understanding of emotion and life.