"I Smile Back" is very nearly as raw and unsparing as a film not ending in a bloodbath can get. Like its lead character, it feels everything just a little too deeply, the sweet intermittent highs suffocated by an anguish from which escape seems to be unreachable. Cinematic depictions of suburban dysfunction are almost as old as the medium itself, but this particular story, stunningly directed by Adam Salky (2009's "Dare") and written by Paige Dylan & Amy Koppelman (based on Koppelman's 2008 novel), is treated with such aching care and uncompromising vitality it might as well be the first of its kind. At its steadfast center is comedienne Sarah Silverman (2014's "A Million Ways to Die in the West"), her transformative dramatic performance nothing short of monumental. She has dabbled in serious fare before—her supporting turn in 2012's "Take This Waltz" was eye-opening—but embodying the self-destructive, mentally ailing Laney is a bold leap forward in proving how much more there is to her than simply an acerbic, frequently typecast actress who can successfully land a joke.

Stay-at-home mom Laney Brooks (Sarah Silverman) fiercely loves her children, Eli (Skylar Gaertner) and Janey (Shayne Coleman). She wants to be the devoted, caring wife she knows her husband, motivational insurance guru Bruce (Josh Charles), deserves. Behind closed doors, however, she is barely keeping it together, wrestling with so many demons—depression, alcoholism, drug addiction, adultery—she's long lost count. With one part of her mind stuck in the sadness of her past and another part filled with anxiety over what her future might hold, Laney wears a cracking visage of normalcy in her present. There is no disputing her kids mean the world to her, which only makes her feel more guilty about the turmoil she is experiencing and the ways in which her behavior could damage their emotional development. When a late-night substance binge leads her to commit a perverse sexual act on her daughter's bedroom floor, it is her apparent, long-coming rock-bottom. Laney agrees to a stay at a rehab facility, but finds it difficult to confront with her therapist (Terry Kinney) the underlying roots which have led her to her escalating troubles. Once she returns home, she makes a newly sober go at picking up with her domestic life. She is not well, though, and no one-month sojourn in the country was ever going to be able to mend the deep-seated problems continuing to plague her.

"I Smile Back" does not judge Laney or present a one-sided character profile. The film—a prime conversation-starter rich in ambiguity, suggestion and compassion—sees her in all her wounded beauty, a tragic human figure who isn't one way or the other, but everything at once. Laney is not a terrible person, and, if anything, she is the opposite of aloof. She lies to her family about what she does when they aren't looking, but she loves them all the same, purely and passionately. Awash in a hopelessness she cannot quite place, she self-medicates with booze, cocaine, and mid-day motel rendezvous with married friend Donny (Thomas Sadoski), who tells her he loves her even as they both know there is no future in their tawdry sexual relationship. When Bruce brings home a puppy, Laney wants nothing to do with it; instead of seeing a cute animal in need of a home, she sees a living creature who will die in approximately ten years and break all their hearts. Indeed, she cannot bear to consider death in any form, yet cannot seem to choose life for herself, either. Her "daddy issues," as she flippantly calls them—her estranged father (Chris Sarandon) walked out when she was 9 and now lives in Upstate New York with a new wife and child—is the rotten icing on the cake. Whether she wants to admit it or not, this resulting feeling of abandonment plagues her, casting a mirror on her own fears of parental inadequacy.

Sarah Silverman's work is of a towering caliber few actors could even dream of reaching, so emotionally piercing and yet so bereft of vanity and artifice it has the power to haunt the viewer for days. In front of the camera for very nearly every frame, Silverman has brought to daring, startling life a character in crisis, in grievous need of help. If Laney has a short fuse when made to feel less than—as when she is denied entry into her kids' school after forgetting her identification at home—even her explosive reactions tend to take place in private. By and large she is a kind person, which only adds to the disparity of her seeming one-track mission to demolish everything good in her life. Mind, body and spirit, Silverman gives herself over to this demanding part, not a shred of the performer's public persona remaining.

Josh Charles (2007's "The Ex") essays a poignant, layered role in his own right as husband Bruce, a man who instructs others on how to live—he has recently released a book he somewhat pompously describes as "a Bible for the here and now"—but chooses for a long time not to recognize Laney's problems. These are not two people who have fallen out of love—following rehab, he tells her he would marry her a hundred times over—but he does have a breaking point and is devastated as she continues her increasingly transparent deception. When Bruce finally confronts her, Charles unleashes a guttural sorrow over the demolition happening before his eyes. Laney has returned to taking her prescription lithium to balance her mood swings, but it has long since stopped working. Nothing works. As much as Bruce wants to be a beacon of support, he knows Laney is the only one who can take the steps necessary to help herself. Sadly, things may not end the way he wants.

A showcase for Sarah Silverman's breathtaking range as an artist but also so very much more than that, the brutally candid "I Smile Back" holds a disquieting profundity seeping from each successive frame. In concept, Laney has it all—well, almost all, as her own professional aspirations have been tabled as her family has taken shape—but none of it can mend the abyss of despair and addiction eating at her soul. When she looks out from her eyes, she spots hypocrisy and disappointment and the tragedy of people going through the paces of a routine existence where no happy ending exists. Her therapist tells her the morsels of joy and transcendence which organically reveal themselves in between the tough stuff are worth waiting for, but whether or not she holds on long enough to see the light has yet to be foretold. To witness Laney's journey in all its simultaneous empathy and ugliness is to stare into a darkness where the illuminated exit signs have nearly flickered out. She's neither good nor bad, selfish nor cruel, apathetic nor deserving of an unfortunate fate. Yes, she smiles back, but what is hidden behind this socially expected nicety is masterfully, joltingly, harrowingly portrayed.