Secret coders / Yang, Gene Luen

"Hopper never dreamed that there was a connection between the Bee School and her missing father--but it turns out that Albert Gracie was also a student of the mysterious coding school. His disappearance can only be the work of Dr. One-Zero. Once a star pupil of the Bee School, Dr. One-Zero is now a green-skinned villain on the hunt for 'the most powerful turtle in the world.' And the coders may be the only ones who can stop him"--Back cover.