Hae-jun discovers a time machine while Yoon-young struggles with her busy job until tragedy strikes.

Yoon-young thinks that it could be a good thing that she somehow ended up in 1987 and met Soon-ae.

Yoon-young joins Soon-ae's class as planned, but a sudden twist drastically disrupts everything.

Hae-jun's expectations are challenged as events unfold, until a student teacher enters the scene.

Yoon-young's choice to withhold the specifics of her reasons for staying might have been an error.

Despite Hae-jun's confidence in his thorough preparations, it turns out they are insufficient.

Hae-jun and Yoon-young find relief, but their narrow focus may lead to unforeseen consequences.

The truth dawns on Hae-jun and Yoon-young that they are bound by certain inescapable factors.

Despite grappling with the grief of her sister's death, Soon-ae's primary concern lies with Hee-sub.

With an awareness of how small details can alter everything, Hae-jun directs his attention to Hae-kyung.

The complexity of the case deepens as Hae-jun and Yoon-young investigate, causing confusion to mount.

Hae-jun is caught in an unfortunate coincidence, with everything pointing to him as the murderer.

Hae-jun realizes that investigating the case might have affected someone very close to him.

Looking into the eyes of the culprit who stands staring down at Hae-jun leaves him speechless.

Farewells exchanged, Yoon-young and Hae-jun journey to meet them again on the other side of the timeline.