In the spring of 1776, thirteen-year-old Elspeth Culpepper wakes to the terrifying sound of cannons. The Siege of Boston has begun, turning her once-quiet city into a chaotic and dangerous war zone. With her father, her only living relative, suddenly missing, Elspeth is left completely alone. Desperate to avoid the orphanage, she wanders the broken streets searching for work and a way to survive. But the war is not the only threat looming over the city. A deadly smallpox epidemic is sweeping across Boston, forcing citizens to fight an invisible enemy alongside the visible one. As panic rises and a crude, controversial vaccine divides the town, Elspeth uses her own immunity to find work caring for Abigail Adams and her family. Amidst the raging revolution and the terrifying outbreak, Elspeth must navigate a world turned upside down. Will she be able to survive the siege and finally reunite with her father?