Ivan (Ashton Kutcher) had a bad childhood, because his behavior caused a disaster, which made his childhood full of unbearable memories. In fact, he only vaguely remembered some terrible scenes, which have been entangled with his normal life. Ivan accepted the advice of the psychologist to record the trivial life in the notebook, but accidentally found that he could go back to the past through the notebook. Only then did he clearly remember that he had done so many wrong things in his childhood. He fantasized about using his current consciousness to sneak into his childhood body to make up for the harm caused to people by all kinds of mistakes, especially hoping to get back together with Casey, who he had a crush on back then. However, his changes across time and space again and again can only lead to more and more hopelessness in the real world. Everything is like a butterfly effect, which moves the whole body.