Do you dream of a city at the end of time? In a time like the present on a world that may or may not be our own three young people-Ginny Jack & Daniel-dream of a fabulous decadent city in the distant future: the Kalpa. The dreams of Ginny & Jack overtake them without warning leaving their bodies behind while carrying their consciousnesses forward into the minds of two inhabitants of the Kalpa-a would-be warrior Jebrassy & an inquisitive explorer Tiadba-who have been genetically retroengineered to possess qualities of ancient humanity. In turn the dreams of Tiadba & Jebrassy carry them back into the minds of Jack & Ginny. As for Daniel: he dreams of an empty darkness--all his future holds. But more than dreams link Ginny Jack & Daniel. They are fate-shifters born with the ability to skip like stones across the surface of the fifth dimension inhabiting alternate versions of themselves. & they are each guardians of an object whose origins & purpose are unknown a gnarled stony artifact called a sum-runner that persists unchanged through all versions of time. They can save the future but they are being hunted down.