As the delicate fiber of time breaks and the clock rewinds, Kim Seokjin is repeatedly thrown back to the fateful date of April 11. Upon returning to Korea after two years of absence, Seokjin is tragically reminded of his once carefree group of high school friends. They were inseparable, the only light in each other's lives—until they went their own sorrowful, separate ways.

Finding Kim Namjoon in prison for assault, Seokjin learns the harrowing truth: Jeon Jungkook and Min Yoongi are dead; Jung Hoseok had a horrible accident; Park Jimin is missing; and soon, Kim Taehyung is found with his father's blood on his hands. But a serendipitous opportunity allows Seokjin to travel back in time and save his friends. Yet each time he takes a leap, reality slightly distorts—and Seokjin wonders if there will ever be a world where the seven of them can be happy together again.