After a flu sweeps the country and leaves most of the population dead, Georgie cares for her two younger sisters and worries for their cystic fibrosis: Annalee had lung transplants before the epidemic and only needs medicine, while Eliza is severely ill. They stay in their house, self-quarantined.
A call comes from the hospital, informing them they have lung transplants ready for Eliza. The sisters travel into inner Melbourne, where they meet a girl, Mari, with an unnamed baby. Mari leaves the baby with them and commits suicide as they're about to reach the hospital.
The hospital is bombed-out, and Eliza reveals that the phone call was a recording she kept from before the epidemic. Annalee is growing more ill as her body rejects the lung transplant, and they're running out of medicine. Eliza faked the calls to get them out of the house. As Georgie begins to despair, the phone rings.
In city that depends on highly trained singers to keep their clockwork machines in perfectly working order, one such singer, Siri, comes up against a chaos-maker, a man of power who despises the predictability of clockwork.