Set during the Great Depression, a resourceful twelve-year-old named Aaron struggles to survive in St. Louis after his mother is sent to a sanitarium and his father leaves town for work. Living alone in a shabby hotel filled with eccentric tenants, Aaron resorts to various schemes to sustain himself, including selling homemade sets of marbles. He tries to maintain appearances at school and among friends, while his younger brother Sullivan is sent away to live with relatives. As the adult world weighs heavily on him, Aaron faces eviction and the looming threat of being sent away from his beloved home.

In his quest for survival, Aaron befriends Lester, a kind but down-on-his-luck bellhop who becomes a mentor figure. With Lester's help and his own ingenuity, Aaron navigates the complexities of poverty and isolation. Despite his efforts to keep his life intact, the pressure mounts as the hotel's future becomes uncertain and dangers close in. Through acts of bravery and clever thinking, Aaron manages to find moments of hope and friendship amidst the bleak circumstances.