Cornwall. Last year. Amy and Jack are on the final day of their honeymoon and enjoying a last scuba dive when Amy sees an object on the sea bed. She tries to get it, but in doing so her foot becomes trapped in old fishing line. Jack is unable to free her and goes for help. Meanwhile Amy's air tank runs out... So begins an intriguing tale of mystery and adventure which spans the centuries. The object Amy found once belonged to the Elizabethan mystic John Dee, who used it at the Queen's behest to avert a national catastrophe. As Amy and Jack investigate it they become aware of its strange properties and the forces it can exert on the unwary. An unnamed foreign power learns of Amy's find. They know its potential, want it for their own ends, and will stop at nothing to get it. British intelligence becomes aware of what's going on and determines to stop them. Amy and Jack are caught in the middle, pursued by both sides. They are challenged to their limits, until they must make a decision which will change the rest of their lives. The action switches between the present day and Tudor England in this tense thriller which will appeal both to fans of historical novels and to readers of Dan Brown and Tom Harper.