Skye Cassidy has just celebrated her twenty-first birthday when a deadly flu-like illness begins sweeping across the country. Before long the hospitals are overwhelmed and entire areas have been quarantined. Soon after that, the utilities fail and gas and food become scarce as the sickness reaches epidemic proportions, causing the critical infrastructures to collapse and transportation to grind to a halt.
Skye continues to live while people around her fall victim to the mysterious illness, and struggles to adapt to her increasingly lonely existence. Finally, in desperation, she sets out on a journey, following the faint sound of a faraway voice on the radio.