Two Brooklyn teenage prodigies, C.J. Walker and Sebastian Thomas, build make-shift time machines to save C.J.'s brother, Calvin, from being wrongfully killed by a police officer.Two Brooklyn teenage prodigies, C.J. Walker and Sebastian Thomas, build make-shift time machines to save C.J.'s brother, Calvin, from being wrongfully killed by a police officer.Two Brooklyn teenage prodigies, C.J. Walker and Sebastian Thomas, build make-shift time machines to save C.J.'s brother, Calvin, from being wrongfully killed by a police officer.