Fear overshadows the thrill of visiting a new map when an unexpected character creates chaos for the Crafters' Club. Held prisoner, Charli must rely on the quick wit and resourcefulness of her friends if there is to be any hope of escape. Find out which map is chosen, who the mysterious character is, and what unimaginable difficulties the four friends face in this fast-paced adventure. The Professor is the fourth book in The Crafters' Club Series.