BC Purple B/2C Ben 10 A Small Problem

This title is part of Bug Club, the first whole-school reading programme that joins books with an online reading world to teach today's children to read. In this Purple-B level Ben 10 book: Ben has the Omnitrix. His biggest enemy, Vilgax, wants it. When Ben turns into Grey Matter and is kidnapped, Gwen and Grandpa have to track him down. How can they save him from evil Enoch?