The tiger's egg - Jon Berkeley

Miles and Little are now part of the Bolsillo brothers' circus, which features the mysterious Dr. Tau Tau as one of its main attractions. When Miles and Dr Tau Tau go in search of information surrounding Miles's father, they are captured by a gang known as the Fir Bolg, who are looking for a powerful Tiger's Egg. Miles becomes involved in an extraordinary quest, which confronts him with the talking tiger once again. He also learns the true story behind his parents, their connection to the circus, and to the Egg. Meanwhile, the Great Cortado is on the loose and is looking for the Egg. But when the Egg's location is finally discovered, there are surprises in store for everyone...