Hunter Steele falls through a hole and suddenly finds himself in a strange new world: inside Earth itself! This inner world is threatened by the evil Invectids, but they are kept at bay by the mighty people known as Spider Riders. Soon afterwards, Hunter meets a battle spider named Shadow; and through a series of events, he discovers that he too is a Rider, and Shadow is his new partner. Hunter decides to fight alongside other Spider Riders such as Corona and Igneous to defend against the attacks of the Invectids – but all is not well. It has been foretold that the arrival of an Earthen (such as Hunter) will herald disaster for the inner world. One question remains: will Hunter cause the disaster, or will he save them from it?