In Book Two in the Ring of Five trilogy, Wilsons Spy Academy has called back their most brilliant trainee spy: Danny Caulfield. Danny is to be sent on an urgent mission: to find the treaty stone that protects the Upper World before the Ring of Five, leaders of the Cherbs, destroy it and wage war. Danny and his friend Dixie - a spy who can appear and disappear at will - must set off the Kingdom of Morne to save the stone. But the Cherb children have got there first, and the King of Morne pits Danny against them in a contest for the stone. Lily, a Cherb, reveals to Danny that she is his sister: she urges him to join the Ring of Five with her. Danny is locked into a battle between the two worlds and with himself. Who's side is he on? Wilsons or the Ring of Five? And how much can he truly trust Lily?