The novel is set in Solis, a city where time is a tangible, glowing currency on one's skin. A young boy, Kael, is driven to desperation as he watches the life-light of his sister, Elara, rapidly fading. He resolves to undertake an impossible heist: to steal a portion of the endless time hoarded by the city's immortal rulers, the Temporals, from within their impenetrable fortress, the Aethelgard. After forging an alliance with a disgraced architect, Kael successfully infiltrates the tower and steals a powerful Temporal Key. He soon discovers his prize is not a cure, but a curse. The raw, unfiltered time is a destructive force that would annihilate his sister. His only hope is to find the Whispering Sundial, an ancient artifact capable of purifying the stolen energy. In a frantic race against his own dwindling light and the city's closing security net, Kael learns the sundial requires a sacrifice. He must give the last of his own life to the machine, becoming a memory in order to fuel the miracle that will grant his sister an eternity.