Otto Anderson, a widower 63 years old, resides in a rowhouse in a Pittsburgh, Pennsylvania, suburb. He always has a clean, tidy, and perfectly disciplined lifestyle, following all the rules in and out of his home. Otto lost his wife, Sonya, a teacher, six months ago. Now, Otto has turned into a bitter, meticulous curmudgeon. He notices a fearless cat near his garage. He works in a steel company and is forced by his manager to resign from his job. He cancels his utilities, like gas and electricity, and wants to commit himself to joining his deceased wife.
Otto is about to hang himself and is stopped by the arrival of new neighbors, Mrs.Marisol, a pregnant lady, and her husband, Mr.Tommy. They were troubled to park their car back up on the trailer. Otto helps him out of irritation as they have already done enough. He gets introduced to their kids, Abby and Luna. Marisol offers the dish she made and puts an effort into getting to know him. After tasting it, he tries to hang himself, but the noose slips loose from the ceiling. Otto visits Sonya's grave and remembers their earlier times: He was turned down for the army as a young man because of his hypertrophic cardiomyopathy, and then he met Sonya on a train when he followed her to hand over the book she dropped. She gave him a 1964 silver quarter during the ticket checking, and he has kept it ever since.
Again, he finds the cat on his veranda. Marisol and Tommy knock on his door again and ask for a ladder. She also offers him some cookies to taste. Otto finds the same cat under his car and moves it out of the garage. Even though he harbors resentment towards Anita's husband and Otto's friend Reuben, a stroke survivor who is non-responsive, Otto assists Anita with her radiators. Otto continues his second suicide attempt in his garage while reflecting on his and Sonya's courtship. For God’s sake, Tommy breaks his leg after using Otto's ladder as a sign of saving Otto’s life. Marisol asks Otto for help taking her to the hospital after Tommy’s ambulance. Otto drags Marisol and the kids to the hospital. Against Marisol's will, he beats up a clown for stealing his quarter during a magic trick in the hospital.
Marisol finds the stray cat in its dying condition. Jimmy saves and decides to provide shelter and take care of it. Otto’s memories reflect his graduation day from engineering school, and he proposes to Sonya. He tries another suicide attempt while he stands on a railway platform. But instead, he saves an old man who unexpectedly fell over the rails. At the last second, he allows himself to be dragged to safety by a stranger. Otto grudgingly accepts the stray cat that Jimmy saved from the streets after discovering he is allergic to it. He then takes the cat to Sonya’s grave and spends some time there. The cat occupies Sonya’s space in the bed. The child recognizes Otto as his former teacher's spouse and relates how Sonya helped him as a transgender student when Otto confronts Malcolm, a teenager, for distributing unwelcome advertising circulars.
Marisol's inability to drive irritates Otto, who teaches her with complete patience. They go to Sonya's favorite bakery, where Otto recounts that Anita and Sonya used to be closest friends but that he and Reuben fell out over minor issues like their allegiances to various automakers, which led to Reuben's "coup," in which he took over Otto's position as chair of the neighborhood association. While Marisol and Tommy go out for the evening, Otto watches over Abby and Luna. He also makes friends with Malcolm and fixes his bicycle.
Following the virality of the footage of the altercation at the railway station, social media journalist Sharie Kenzie meets Otto to interview him. But he avoids the journalist. Otto couldn’t accept Sonya's passing and lashed out at Marisol and a representative of Dye & Merika, a real estate firm trying to take over the neighborhood. Out of despair, he closes the door and stops speaking to Marisol, who is deeply worried about him. He gets ready to shoot himself in the head while recalling the Niagara Falls bus disaster that resulted in Sonya losing her unborn child and becoming paralyzed. When Otto gets up to kill himself, Malcom bangs on the door. After being asked to leave by his father, Otto agrees to let Malcolm stay for the night.
Otto discovers that Dye and Merika are working together, with Reuben and Anita's estranged son, to buy their house and place Reuben in their nursing care by using Anita's covert Parkinson's diagnosis. He goes to Marisol’s house and asks for a mobile to make a call. Marisol, who is still angry with him, behaves rudely and asks why he behaved in such a way. He finally explains Sonya's stillbirth and disability. He also admits to trying to kill himself with Sonya. His dissatisfaction with the Dye & Merika housing complex's accessibility and how he was ousted as association chair following a contentious argument with the corporation led to this. He then vows to fight them and asks Marisol for assistance. The neighborhood comes together to stop Dye & Merika workers from taking Reuben when they arrive, with Kenzie disclosing their unauthorized access to Anita and Otto's medical information.
Otto passes out and names Marisol his next of kin before being brought to the hospital. After learning that "his heart is too big," she finds it amusing, goes into labor, and gives birth to Marco. Otto gives Malcolm his car, gives Marisol and Tommy the crib he created for Sonya when she was expecting, and gets closer to his neighbors. Three years later, Tommy sees that Otto hasn't cleared his walkway. He and Marisol discover Otto passed away from heart failure and that he left Marisol a letter describing his house, savings, new truck, and cat and asking her to take care of all those. The neighbors assemble to commemorate Otto following his request for burial.
