The Ring of Five, ruthless leaders of the Lower World, are growing stronger. Wilsons spy academy is the only force left protecting the Upper World and its power is fading. They must find a spy to infiltrate the Ring, one who has the mark of the fifth, one who has treachery written on his heart. Danny is on the way to his new boarding school when he is kidnapped. He has been handpicked to join Wilsons, dedicated to the defeat of the ruthless Cherbs led by the Ring of Five. Danny makes friends and settles into his rigorous spy training. But with his different coloured eyes and his pointed features, he looks like a Cherb, attracting enemies and several attempts on his life. But no danger compares to the mission that Master Devoy sends him on: Danny must reach the Lower World to infiltrate the Ring. He is determined not only to be the best spy but to keep his friends. But he is soon to discover he can trust no one, not even himself...