In a city where sunlight rarely touches the streets and a lethal plague spreads like rot, Arin scrapes by as a street-level courier. She delivers letters, dubious remedies, and false hopes to those who can still afford them. But when she glimpses a mysterious figure bounding across the rooftops-rumoured shadow couriers said to carry real medicine-Arin is drawn into a world above the city's gloom. Whether they're saviours, thieves, or something else entirely, the secret they guard could shift the balance of power...if it doesn't destroy her first.