Former high school cheerleading captain Rose Lorkowski (Adams) is a thirty-something single mother who cleans houses for a living. Wanting to send her trouble-making eight-year-old son Oscar (Jason Spevack) to a private school, Rose decides to take her married lover's advice and get into the "lucrative" business of crime scene clean-up. Rose convinces her disillusioned, underachieving sister Norah (Blunt) to join her in the enterprise, which she calls "Sunshine Cleaning." The sisters begin to find meaning in their function to "help" in some way in the aftermath of a loss, just as the job stirs up memories of their own mother's death. Their priorities and goals tested, Rose and Norah face hard challenges as they strive to improve their lives.