Hyeong Ju, while living an ordinary detective life, loses one of his closest colleagues, which in turn takes away all his motivations to live. This is when he receives a phone call from an unknown caller telling him that he can go back a year in time as long as he is willing to do so. Hyeong Ju decides to take his chance of traveling back in time to save his colleague.

What seemed to be a free opportunity for a better life sends Ga Hyeon into a downward spiral when she finds her friend, Ju Young, as the victim of exactly the same accident that she got into. Ga Hyeon then immediately seeks Lee Shin’s help to see if there is a chance to undo what has already happened to Ju Young.

The police find the dead body of Yeon Soo at the park where she met with Ga Hyeon on the night before. When Ga Hyeon is summoned to be questioned as a testifier, she has no choice but to hide the details regarding the reset. Missing puzzles in between Ga Hyeon’s testimony leave the detective in doubt, but in the end, an alibi that makes it impossible for Ga Hyeon to be the murderer gets confirmed.

Ga Hyeon and Hyeong Ju eventually get in touch with Jung Tae and in doing so, they find out his relationship with Jeung Seok. However, as more they look into the mysterious deaths of the resetters, the clues somehow direct them toward Lee Shin. Ga Hyeon, in the end, decides to visit Lee Shin just to find out she has left the country.

When the resetters gathered at the meeting organized by Lee Shin, they get a basket of flowers with a memo pointing to the next target. Ga Hyeon and Hyeong Ju then search for the flower shop that made the exact flower basket like the one delivered to them. As they get closer to finding the answer, an unexpected clue stumbles upon them.

It turns out that the bouquets were sent by Ms. Song under Lee Shin’s order but when Ga Hyeon and Hyeong Ju found out about it, Lee Shin was already gone. Meanwhile, what was thought to be an arson was just a mere accident at the flower shop. Moreover, Hyeong Ju finds out that Park Young Gil, the first resetter who died in a car accident, has a twin brother.