Young Tracy Richards, played by Louanne, enjoys playing basketball with her neighbor Shingo, portrayed by John Louie, until her divorced father, Don Richards, played by David Birney, arrives in his fiery red Jeep to take her on a special outing. Before they leave, Don's ex-wife and Tracy's mother, Paula, played by Suzanne Pleshette, reminds him to return Tracy at the agreed time.
During their meal of Chinese food, Don expresses his annoyance with the plot of a recent science-fiction movie. In contrast, Tracy shares her thoughts on the significance of believing in the intangible. When Don steps away to make a phone call, Tracy opens a fortune cookie that reads: > "Meet me in the lounge. - God." A second fortune cookie reinforces the message: "I mean you, Tracy. - God."
In the lounge, Tracy hears a man's voice calling her from behind a red lacquer door. He introduces himself as God and asks for her assistance. Initially skeptical, Tracy suspects her father is playing a prank, but upon realizing that no one else can hear God's voice, she becomes a firm believer. God praises her when she speaks about the importance of faith in unseen phenomena before his voice suddenly fades into silence.
On their drive home, Tracy mentions having a vague daydream, but Don, who is an advertising art director, reassures her that daydreaming is commonplace. He leaves her in the car briefly to grab work from his office, where God appears unexpectedly in the backseat, taking the form of an elderly man played by George Burns, dressed casually in a gray jacket, black-rimmed glasses, and a red shirt. When Tracy expresses her surprise at his appearance, expecting a divine figure in robes, God humorously quips that she has mixed him up with actor Charlton Heston. He laments the diminishing belief in him and seeks Tracy's help in coming up with an advertising slogan to disseminate his message, appealing for one that resonates with children. Don later chimes in with tips for crafting effective slogans.
Back at home, Tracy inquires with the housekeeper, Rosa, whether she speaks to God. Rosa acknowledges her daily prayers but suggests that Tracy's vivid imagination might be at play rather than a direct encounter. Subsequently, Tracy shares her divine experience with Shingo, who remains skeptical. However, when Tracy throws a basketball and scores a perfect shot, Shingo begins to question her story.
At school, Tracy's teacher, Miss Hudson, reprimands her for being inattentive and not submitting her homework, leaving Tracy unable to articulate her disinterest. Back home, she becomes fixated on television commercials in her quest to devise a fitting slogan for God. During an episode of The Johnny Carson Show, God again materializes, this time directly in Tracy's living room, extending her deadline for the slogan with the suggestion to collaborate with Shingo, eventually leading to the tagline, "Think God."
The next day at a local McDonald's, Tracy presents her slogan to God, who explains that the next phase involves spreading the word. Despite her concerns about falling behind in schoolwork due to the added responsibility, God encourages her to proceed, resulting in Tracy rallying her classmates to create posters and chalk messages throughout the town. However, Paula receives a letter from Miss Hudson, prompting her to confront Tracy about her claims of divine visitation. When Tracy insists on her experiences, Paula, in disbelief, pushes for her daughter to focus on her studies while Shingo brings in his cousins to help promote the campaign.
Later, as school authorities intervene, Tracy feels overwhelmed, voicing her frustrations to God about the consequences of her actions. God comforts her by magically completing her math homework. As her parents probe her about the situation, Don leans towards seeking help from a psychiatrist, while Paula wishes to manage things internally. They resolve to monitor Tracy's behavior for a few days.
At school again, principal Mr. Benson organizes a meeting regarding Tracy's persistence in her God campaign. When threatened with expulsion, she agrees to cease her activities if God consents to the plan. However, after learning of her divine encounter through a fortune cookie, the principal suspends her, citing the need for professional intervention.
In a twist of events, Tracy’s friends stage a picket in support of her return to school. In response, Don and Paula take her to see Dr. Jerome Newell, played by Anthony Holland, who conducts tests to evaluate her mental state. His assessment suggests that Tracy has created an imaginary father figure to cope with the absence of her real father, and he proposes she enter a mental health facility in Santa Barbara. Amid the pending treatment, Tracy searches various places of worship for God but finds no trace of him.
Driven to desperation, Tracy decides to run away, with Shingo assisting her in hiding at his grandparents' house. However, upon learning Don's confrontation with Shingo, Tracy evacuates to the Union Train Station. Here, God finally shows up, driving her home in a motorcycle sidecar after effectively evading two pursuing policemen. When Tracy's parents discover her safely back in bed, she explains how God guided her home.
As the story unfolds, news spreads about Tracy's popular slogan gaining international acclaim. In court, a judge orders a panel of psychiatrists to evaluate her mental condition. As their conclusion leans toward treatment, God surprises everyone by appearing as Dr. Stevens, a psychiatrist. He showcases his powers by making a chandelier vanish and twist day into night before mysteriously departing. The stunned panel is left devoid of words as the Richards take Tracy home.
In a heartfelt conclusion, the Richards celebrate at their favorite Chinese restaurant where Tracy receives a new message from a fortune cookie, leading her to the lounge. There, God expresses gratitude to Tracy and her friends for their extraordinary campaign, leaving her wistful yet hopeful as he promises to reach out if he faces a significant challenge in the future.
