Books with title Wizard for Hire, Book 3: Magic Required

Ozzy and his friend Sigi are in more danger than ever before. After being injected with the mind-controlling serum his parents created, Ozzy is learning to control the minds of people, but he is still being hunted by Ray, the power-mad villain who will stop at nothing to find and possess the formula. And on top of that the wizard Rin is missing, leaving Ozzy to wonder once again if magic really does exist. When it becomes apparent that the minds and free will of all mankind are in danger of being controlled by whoever controls the serum, Ozzy and Sigi join forces with four new friends that claim magic-like abilities. When Rin finally returns, Ozzy will discover once and for all what happened to his parents, what really happens at those popular fantasy conventions, and if magic truly exists.