Retired CIA agent Barbara Gold decides to take up gardening to pass the time in Cheerville, a quaint New England town. Before she can pay for her peat moss and a copy of Gardening for Numbskulls at the garden shop, she overhears two ladies gossiping about the death of Cheerville's best gardener.

Based on her extensive secret agent training, Barbara quickly concludes Archibald didn't die in a freak accident via hedge clippers, but was murdered. The local police are no help, ruling the death a suicide. To solve this case, Barbara must go undercover on her own—with a 9mm pistol, of course.

From taking Seniors Yoga to infiltrating an underground gambling club, Barbara must use her best asset—her guise as a sweet seventy-year-old granny—to find the murderer, while not letting her babysitting duties to her thirteen-year-old grandson, Martin, and attention from a new love interest distract her.