The Subterranean Stratagem — Michael Pryor

This second book in the series has Kingsley chasing after his past to solve the mystery behind his birth and save the world once more

Kingsley Ward and Evadne Stephens are the Extraordinaires and they should be the toast of the town -- but their juggling and escapology act is failing and Kingsley is to blame. His wolfish side is breaking free, ruining performances, and endangering those around him. The secret to controlling this wildness lies in his mysterious past. Was he really raised by wolves? Who were his parents and what happened to them? The discovery of Kingsley's father's journal promises answers, but when it is stolen the Extraordinaires uncover ancient magic, a malign conspiracy, and a macabre plot to enslave all humanity. What begins as a quest to restore Kingsley's past becomes an adventure that pits the Extraordinaires against forces that could shatter the minds and souls of millions.