Sarah Silverman, with Josh Charles, gets serious in the familiar addiction story “I Smile Back.” (Broad Green Pictures)

Sarah Silverman delivers an impressive dramatic turn in “I Smile Back,” in which the comedian and actress plays a wealthy homemaker hiding a prodigious addiction to drugs and alcohol behind the curtains of her picture-perfect McMansion.

Married to a terrific guy (Josh Charles) and devoted to her two kids (Skylar Gaertner and Shayne Coleman), Laney Brooks fulfills the role of wife and mom convincingly, drawing crayon pictures on her children’s lunch bags every morning and insisting on escorting them to class. But what looks like maternal doting on the surface masks a crippling fear of abandonment and anxiety that Laney banishes by self-medicating. She sips vodka into the night (and drunk-dials a rival mom), snorting cocaine while hubby and the kids shoot baskets outside.

Directed by Adam Salky from Amy Koppelman and Paige Dylan’s adaptation of Koppelman’s 2008 novel, “I Smile Back” follows the expected downward spiral of an addiction narrative, complete with boozy acting-out, rehab, the inevitable backslide and a gruesome sequence in which Laney hits rock bottom. Although the plot is painfully familiar — and not particularly edifying, compared with similar narratives that have gone before — the novelty here is Silverman, who doesn’t exactly erase her comic persona so much as bring to the surface an inherent darkness that has always lurked in the shadows.

Viewers who witnessed her supporting performance in the 2012 drama “Take This Waltz” won’t be surprised that she has the chops to sustain a lead performance. Still, this feels like a breakout for an actress poised to join Kristen Wiig as another famous funny lady capable of plumbing astonishing depths of vulnerability and inner sadness. If “I Smile Back” accomplishes anything, it proves that Silverman is no joke.

R. At the Angelika Pop-Up at Union Market. Contains strong sexual content, substance abuse, disturbing behavior, and profanity. 85 minutes.