A genius dog, Mr. Peabody, adopted an orphan and named him Sherman. Sherman is very dynamic in class and good at history, that makes teacher and his friend surprised except Penny. In one time visiting Sherman’s house, he reveals by accident the reason why he is good at history: The time machine. The troubles come when Sherman and his girlfriend used it to go back to the past and changed the history that makes the future change, too. Recognizing this, Mr. Peabody comes back to the past with the children and try to fix the mistakes.