In the summer of 1942, widower Eddie Kurnitz drives his young sons, Jay and Arty, to Yonkers, New York, to see their stern German grandmother for the first time in several years. Intimidated by his own mother, Eddie leaves the boys to wait in the family candy store while he goes upstairs to announce their arrival. Before long, Jay and Arty spot their daffy and emotionally volatile Aunt Bella absentmindedly wandering outside on her way home from the movie theater. After speaking with his mother, Eddie admits to having gone bankrupt paying for his wife’s medical bills. Although he has borrowed $9,000 from a "loan shark," he is unsure if he can repay the money unless he accepts a lucrative job traveling the Southern U.S. selling scrap metal for the war. Realizing they have no choice but to stay with their grandmother, Jay and Arty struggle to make a good impression. Grandma refuses, bluntly expressing her disdain for their dead mother, but Bella threatens to leave home unless the boys are allowed to stay. As Jay and Arty acclimate to life with Grandma, Bella develops a relationship with a mentally handicapped movie theater usher named Johnny, who shares her dream of owning a restaurant. When Johnny proposes, Bella excitedly tells the boys, but worries that Grandma will disapprove. While discussing her plans, Bella accidentally reveals that Grandma has nearly $15,000 in savings hidden somewhere in the house. Hoping to borrow the money to help their father, Jay and Arty obsessively scour the closets and cellar before finding their Uncle Louie in the candy store, as he hides from a gangster known as “Hollywood Harry.” Revealing a holster under his jacket, Louie claims to be the bodyguard to a “very prominent public figure,” and offers the boys money to lie if anyone comes looking for him. Over the next few days, Hollywood Harry continues to stake out the house, and Bella grows nervous with the anticipation of telling Grandma about her engagement to Johnny. One night, Louie shows Jay and Arty a secret underground tunnel he and Bella dug as children to elude their mother’s strict rules. Although he relates more stories of Grandma’s abuses, he insists the old woman has “moxie” for enduring her tough German upbringing. On the night Louie plans to leave, Bella prepares a special dinner and struggles to tell her family about her relationship with Johnny. When she mentions the cost of opening their restaurant, Louie becomes suspicious of Johnny’s intentions. Bella, however, declares her feelings for Johnny and fights for her right to start a family and raise children who will love her unconditionally. After her tearful speech, Grandma retires to her room without a word. Later that night, Jay distracts Hollywood Harry, allowing Louie to escape. Meanwhile, Bella moves in with her sister, Gert, and tells Johnny that Louie gave her money for the restaurant. While she is eager to start their life together, Johnny becomes anxious, citing his usual excuse that it is “not a good day” to make any major decisions. Realizing he will never be ready for commitment, Bella decides to make amends with her mother, who insists she should still be treated as a child. Due to Grandma’s emotionally frigid parenting, Bella reveals she often sought affection from boys and young men she met in the park during her youth. Discovering that Bella has acquired the money for her restaurant, Grandma accuses her of stealing and orders her to leave. Bella snidely remarks that her dead siblings, Rose and Aaron, were the “lucky ones” for escaping their mother’s wrath. Hurt by her words, Grandma confesses how their deaths affected her and finally acknowledges that she has wronged her daughter. Bella admits that even though her relationship with Johnny is over, she still wants a life and family of her own. Eight months later, Louie goes on to earn his fortune in Guadalcanal, and Eddie returns from the South. As they say goodbye, Grandma tells Jay and Arty that her savings were hidden under their mattress all along. The boys regret leaving their aunt alone with Grandma, and although Bella earnestly tries to improve her relationship with her mother, the old woman ultimately refuses to change. Early one Sunday morning, Bella leaves home to begin a new life in Florida, where she gets a job waiting tables.