Underneath the teeming city of New York exists a world of massive proportions. Gregor and his younger sister Boots are about to discover the existence of this world and meet the many people and creatures that live there. Following the fantastical discovery will come a grand adventure and the threat to never return home. A choice between love and security will have to be made. Forced to live beyond his years, Gregor will prove that loyalty and hope are worth fighting for.