The one thing that fourteen- year-old Will Burrows enjoys most is digging tunnels. He and his father frequently go on archeological digs to uncover lost items that are sometimes added to his father's museum collection. But when Will's father disappears, Will and his friend Chester embark on a dangerous journey to an underground world known as "The Colony." Will and Chester are shocked to find that there are people living under London with their own set of rules and punishments. Will is certain that this underground society is the reason behind his father's disappearance, but how will two young boys from London survive in this mysterious place, let alone rescue his father?