Taya soars over Ondinium on metal wings. She is an icarus, a courier privileged to travel freely across the city's sectors and mingle indiscriminately amongst its castes. But even she cannot outfly the web of terrorism, loyalty, murder, and intrigue that snares her after a daring mid-air rescue. Taya finds herself entangled with the Forlore brothers, scions of an upper-class family: handsome, brilliant Alister, who sits on Ondinium's governing council and writes programs for the Great Engine; and awkward, sharp-tongued Cristof, who has exiled himself from his caste and repairs clocks in the lowest sector of the city. Both hide dangerous secrets, in the city that beats to the ticking of a clockwork heart.