The following version of this novel was used to create the guide: Alcott, Kathleen. Infinite Home. Riverhead Books, 2015.

In a small apartment building in the heart of New York City, a group of tenants begins to come together as a community in response to the worsening health of their landlord, Edith. Edith has had ownership of the building for years since the death of her husband, Declan, and has done her best to transform it into a space where struggling people who cannot find other leases are able to afford rent. The four tenants are: Thomas, a painter who has suffered a stroke and lost mobility in his hand; Edward, a former stand-up comedian whose career has disintegrated following a destructive breakup; Paulie, a middle-aged man who suffers from a condition called Williams Syndrome and is looked after by his sister, Claudia; and Adeleine, a young woman who has developed a severe case of agoraphobia following the traumatic death of her last partner, N—. As Edith's health fails, the boundaries between the tenants begin to collapse. Edward and Paulie, in particular, begin to forge an unlikely friendship.

The thawing tensions between the tenants of the building lead to the initiation of a romantic relationship between Adeleine and Thomas; after years as a recluse, Adeleine begins allowing Thomas to visit her in her apartment. Even as these relationships begin to form, though, the building begins to face problems when one of Edith's children, Owen, begins urging her to move to a retirement home so that he can take over the building and begin renovating it. Complicating matters is the fact that Edith's unfitness to be managing the building grows increasingly clear; one night, she accidentally allows the heat to go out, a disaster that leads to Paulie's hospitalization with pneumonia. Following this incident, Claudia grows increasingly frustrated with her husband, Drew, who refuses to allow Claudia to take Paulie in; she ends up divorcing him instead, committed to taking care of her brother. Even with the threat of Owen hanging over them, the tenants agree to attend a party that Edith puts on for the building, and Claudia develops a friendship with Edward, whose kindness toward Paulie she admires.

Thomas begins deepening his romantic relationship with Adeleine at the same time as Edward begins spending more and more time with Paulie. When Thomas confronts Adeleine about her agoraphobia, she is quick to point out his dependency on self-harm, and the pair manage to push forward in their relationship as a result. Soon after, though, Thomas learns that Owen intends to evict the residents of the building, and he resolves to find a way to prevent the evictions from occurring so as to protect Adeleine's safe harbor in her apartment. He begins spending time with Edith and pretending to be her husband, Declan, in order to discover that Edith has not willed the building to Owen, but instead to her estranged daughter, Jenny. Thomas leaves for San Francisco without informing Adeleine where he intends to go, and is surprised to learn that Adeleine takes his absence as an opportunity to leave her apartment and begin spending time with Edith.

Claudia and Edward, rather than help Thomas fight the evictions, decide to move out of their apartments and bring Paulie to a location in the Smoky Mountains of Tennessee where a rare and beautiful firefly mating ritual occurs every few years. This leaves Adeleine alone in the apartment building to take care of Edith, a situation that becomes increasingly threatening when Owen catches on to her agoraphobia. Meanwhile, Thomas spends time in San Francisco scouting for evidence of Jenny, and eventually comes across a newspaper article in the library that features a picture of her at a commune in Northern California. He drives up to the forests in the north and finds the commune, but Jenny refuses to speak with him about Edith unless he spends a week at the commune in silence. He agrees to do so, but his absence has dire consequences; Owen breaks into Adeleine's apartment, threatens her sexually, and lords his ability to evict her over her in an attempt to get her to surrender Edith to him.

Claudia, Edward, and Paulie spend an idyllic week in the country waiting for the firefly ritual to occur, and Edward finds resolution with his ex-girlfriend, Helena. Meanwhile, Thomas completes his week of silence at the commune, and Jenny informs him that she has no interest in inheriting the house but would be willing to sign it over to Thomas if he can find a way to transport Edith to the commune to spend her last days there. Thomas phones Adeleine and urges her to bring Edith to California, a task that requires Adeleine to overcome her agoraphobia at long last. When they arrive in California, Edith and Jenny are relieved to be reunited, and Adeleine announces her intention to stay there instead of returning to New York. Thomas goes home to renovate the building, and, after the firefly ritual, Paulie dies of heart failure; the residents of the apartment building begin to work on repairing their lives.