Writer/director Brian Goodman bases this gritty look at a couple of tough guys growing up in South Boston on his own experiences. The reality he brings to the table is what makes this compelling tale a notch above others in the same genre. We first meet Brian (Mark Ruffalo) and best pal Paulie (Ethan Hawke) as they are caught up in a violent armored car robbery. Their entrée into a life of low-level crime is detailed early on in flashbacks in which they are operating under the guidance of a local criminal Pat (director Goodman). Catching up with them in the present day about 12 years later Brian is now married and has two sons while Paulie is determinedly single. Neither has graduated past the workaday life of the average hoodlum and are still taking their lead from the no-good Pat who decides to teach Brian a lesson by gunning him down and leaving him for dead in the snow. Time in prison -- and a conflict between the two friends -- make up the core of the film’s final act when decisions must be made about the eventual paths their lives will take. Fulfilling his promise as one of the screen’s most underrated actors working today Mark Ruffalo gets a three-dimensional role with real guts and complexity. His sterling performance is gritty and finely detailed immersing himself into this low-life loser who is desperately trying -- and failing -- to lift himself up and find a new life. Ethan Hawke is equally fine even if we just saw him play a similar role last year in Sidney Lumet’s similar crime drama Before the Devil Knows You're Dead. Like Ruffalo Hawke completely throws himself into the mind of a Southie and captures the essence of such a character. It’s the two actors’ increasingly conflicted -- and at turns polar opposite -- relationship that makes up the heart of What Doesn't Kill You. Goodman as you might imagine acquits himself nicely in the local criminal role and Amanda Peet nicely underplays Brian’s suffering wife. Donnie Wahlberg (who co-wrote the script) is from that part of the city and adds a good deal of authenticity to his smaller detective role. Brian Goodman an experienced and seasoned actor turns to writing and directing for the first time with remarkably assured self-confidence and a command of exactly what he wants to say. Certainly he’s covering an area he knows well having lived this life in the exact locales in which he’s shooting. With the atmospheric dark gray cinematography of Chris Norr and Robert Hoffman’s sharp editing Goodman’s film delivers with just the right amount of grit and street violence. Mostly though it’s a strong character study. The combination of Goodman’s expertise on the subject and his lead actors’ superlative interpretation pay off in making What Doesn't Kill You so extremely effective. It’s a fascinating and informed look at a place most people will only get to know through the movies.