In the heart of Los Angeles, 93-year-old Thelma Post navigates the intricate challenges of loneliness and dependence amidst a seemingly ordinary life. Her grandson, Daniel, although well-meaning, often suffocates her spirit with his frequent visits and constant assistance, which Thelma finds more condescending than comforting.
Suddenly, a crafty phone scammer seizes the opportunity to exploit Thelma's vulnerabilities. Posing as Daniel, the scammer tricks Thelma into believing that he has been arrested, urging her to wire $10,000 to a local address. In a state of confusion and panic, she complies without realizing the shocking truth: her grandson is perfectly safe, and she has unwittingly fallen victim to a brazen scam.
Determined not to let these fraudsters escape with her hard-earned savings, Thelma decides to take drastic measures. She embarks on a spirited quest to reclaim her stolen funds, despite the protests from her family, including her daughter Gail and son-in-law Alan, as well as the authorities' passive indifference.
As Thelma sets off on this journey of self-reliance, she confronts the harsh realities of aging head-on. Attempting to lean on old friendships proves futile; most of her friends have either passed away or moved away. With a heavy heart, she reaches out to Ben, an old acquaintance living in assisted care, whom she had neglected since her husband’s demise. Together, they brave the treacherous streets of Mona's neighborhood aboard Ben's prized two-person scooter.
Meanwhile, Daniel, along with Gail and Alan, frantically searches for Thelma, their efforts met with frustration. As he vents to his parents about his breakup and the aimlessness in his life, he reveals his deep-seated fears of being trapped in a monotonous existence without purpose.
Thelma's adventure takes an unexpected twist when, alongside Ben, she finds herself lost in a rough neighborhood. Here, tensions mount, and after a heated argument, Ben's scooter is destroyed by an irresponsible driver, leading him to abandon Thelma. Undeterred, she forges ahead alone, only to suffer a painful fall that leaves her in a vulnerable state.
Just when hope seems lost, Ben returns and helps her, mending their strained relationship as they approach their target, only to find a rundown antique shop instead of the storefront they anticipated. Intrigued, Thelma follows a young man who retrieves her money from a PO box, leading them into the cluttered shop where they discover elderly Harvey and his grandson Michael orchestrating a scam operation.
As Ben listens in through their connected devices, Thelma asserts herself, demanding restitution. Harvey, however, refuses while expressing the struggles he faces in managing his failing business. In a dramatic turn, Thelma reveals a gun and takes control of the situation, as Michael attempts to flee. seizing the moment, Ben overpowers Michael, rendering him unconscious as he makes a break for it.
Using Harvey's computer with Ben guarding their captive, Thelma frantically contacts Daniel for help in completing the fund transfer. As they rush to accomplish this task, Michael revives and re-enters, only to face ridicule from Harvey. Struck by the situation, Thelma decides to leave Harvey a portion of the money as a gesture of contempt for his dishonest methods.
With Ben still keeping a watchful eye, Thelma sternly rebukes Harvey about the consequences of deceitfulness and the importance of valuing genuine support. Together, they exit the store, a triumphant sense of accomplishment fueling their spirits as they await Daniel's arrival.
Upon reuniting with her family, Thelma begins to cherish her loved ones more deeply, attending a performance by Ben at the local nursing home, which marks a profound shift in their dynamics. No longer viewing him as merely “soft,” she looks forward to revitalizing their bond.
In a poignant finale, Thelma visits her husband's gravesite alongside Daniel, reassuring him of his capability to navigate life independently when she is no longer around. The film concludes with a touching mirror of fictional and real-life Thelmans, both seated in a car, echoing a scene from the movie—a reminder of their intertwined journeys.
