Order Parts 1 & 2 of Switchers! Includes The Boy Who Disappeared and Rafferty’s Rules.
 
Switchers is about a boy with a gene that allows him to travel (switch) between different worlds. In Part 1, he disappears into a world where genetic modification has gone mad. In Part 2, he must return to this world to rescue not only his friends, but the detectives who investigated his original disappearance.