After a break-up, unemployed recent college graduate Ruby is forced to move back in with her parents, into the rent-free but dismal basement apartment of a posh NYC building where her father, Martin, is the superintendent. The events of the novel take place in one day.
Ruby's oldest friend, Caroline, the trust fund daughter of the building’s penthouse resident, is throwing a party that evening in the penthouse. Growing up, Ruby saw both worlds: Martin's, and Caroline's. Martin's growing resentment of the rich and condescending residents whom he serves manifests itself as the voice of a recently deceased resident, the politically strident anti-capitalist Lily. Martin attributes his fraught relationship with his daughter to the class inequity between his family and the residents, particularly to Caroline.
A homeless woman claiming to be Lily’s cousin appears in the building foyer. Martin asks her to leave the premises. Ruby finds this act heartless, further straining her relationship with Martin. Later, Ruby sees that the homeless woman is still in the foyer, so Ruby lets her inside the building. When Ruby tells this story to Caroline, Caroline exclaims that they should help the woman and enlist the help of her friend Andy, a trust fund beneficiary and photographer who takes artistic photos of homeless people.
That day, through Caroline's contacts, Ruby has an interview for her dream job which, unbeknownst to Ruby, turns out to be an unpaid internship. Martin, during a house call to the penthouse to fix a door, learns from Caroline that the job is unpaid. He tosses a stone for Caroline to catch, but instead it lands in her coffee mug and shatters it. Meanwhile, after the interview, Ruby, disappointed at learning that there is no paying job being offered, takes a walk and bumps into Andy. Andy invites Ruby into his home and offers her money to pose with a rhino head. While posing, Andy gropes Ruby, but Ruby smashes Andy with the rhino head, sending him to the bathroom to clean up his bloody nose. Ruby escapes with the rhino head and abandons it at the Museum of Natural History.
Caroline confronts Ruby about the incident with Andy, defending Andy’s version of events. Caroline also tells Ruby that Martin “freaked out” on her, but promises not to report Martin to her father. Ruby and Caroline argue. Later that evening, Ruby attends Caroline’s party, and confronts Andy, who demands the return of the rhino head. Ruby demands the promised payment for modelling with the rhino head. Ruby takes Andy’s wallet from his pocket and leaves the party.
Ruby returns home and Ruby and Martin both listen to an answering machine message from the property management company, apopleptic at Martin’s incident with Caroline and the stone. Ruby is incensed that Caroline broke her promise to not report the incident to Caroline’s father. Ruby goes to the penthouse to confront Caroline, where she finds Caroline and Andy on the roof with the homeless woman. Andy is photographing Caroline with the homeless woman, and Caroline asks Ruby where she should stand. Ruby advises Caroline to move back a step, which causes Caroline to fall off the roof.
In the epilogue, Martin has moved to Georgia where he works at a new job and lives in a second floor apartment. He is content. Ruby works as a security guard at the Museum of Natural History, and lives with room mates in Astoria. Martin wants Ruby to move to Georgia, but Ruby wants to stay in NYC for now and spend the time growing up and discovering herself.