Yoon Tae Yi and Yoo Min Hyuk time travel from 2050 to 1992 and recover the Book of Prophecy, a book that reveals the tragic end of time travel. However, Tae Yi finds out she is pregnant and decides to stay and have the baby by herself.
After chasing down a suspicious drone, Jin Gyeom thinks he saw his mother when he suddenly gets hit by a car. Jin Gyeom continues to work a kidnapping case involving a mom from the future, hoping it will lead to seeing his mother again.
Agents from Alice try to recover the time card in Jin Gyeom's possession. Jin Gyeom, who thinks Tae Yi is his mother from the future, asks her to take a look at the bizarre card to see if she can figure it out.
Captain Go recovers in the hospital after getting stabbed. Dong Ho manages to handcuff Alice agent Min Hyuk, but he disappears into thin air. Meanwhile, Tae Yi goes through Jin Gyeom's late mother's possessions for additional clues.
After the accident, Jin Gyeom finds himself talking to Tae Yi in the year 2010. He calls his mother and warns her not to leave the house, but it's already too late. Meanwhile, Alice takes note of a time travel glitch.
After meeting with Lee Se Hoon, Jin Gyeom finds a murder case file with a picture of Min Hyuk, an Alice agent, from 1992. Tae Yi triggers something on the time card causing Alice to respond and show up on the scene.
An assassin from the future tries to kill Tae Yi, but Jin Gyeom saves her. The killer leaves a strange, indecipherable formula on Tae Yi's wall. Meanwhile, Seok Oh Won tells Jin Gyeom about The Book of Prophecy.
To keep Tae Yi safe, Jin Gyeom and Tae Yi move into the house Jin Gyeom grew up in. Min Hyuk believes Lee Se Hoon might have the answers needed to find The Book of Prophecy, and Seok Oh Won remains missing.
Tae Yi finds herself in 2021 desperately looking for Jin Gyeom, but he is not alive. With the time card still in her hand, she goes to Oh Seok Won and learns that Jin Gyeom died looking for the last page of The Book of Prophecy.
Min Hyuk shows up and saves Tae Yi from time-traveling sickness, but he doesn't tell Jin Gyeom who he really is. Tae Yi recovers and determines to change Jin Gyeom's future, but no matter what she does, it's just as she remembered it.
After he goes missing for quite some time, Seok Oh Won shows up alive. Meanwhile, Tae Yi confronts Jin Gyeom about the security footage containing Captain Go, and her suspicions grow around him.
A different Seok Oh Won, one who wants to keep time travel possible, takes one step ahead of Jin Gyeom. However, now that Jin Gyeom and Tae Yi know about the last page of The Book of Prophecy, they try to stop time travel.
