Meet Beatrice Zinker: secret code genius and undercover mission expert, who does her best thinking upside down. Hanging from trees by her knees, doing handstands . . . for Beatrice Zinker, upside down works every time. She was definitely upside down when she and her best friend, Lenny, agreed to wear matching ninja suits on the first day of third grade. But when Beatrice shows up at school dressed in black, Lenny arrives with a cool...