Secret relationships are known to be tragic but not as tragic as the one kept by Taeil and Donghyuck who happened to be professor and student which made their relationship forbidden. As well as exploiting Taeil's marriage with his beloved husband, Jungwoo Kim.
When Jungwoo finds out about their secret including Donghyuck's unborn child in Taeil's womb, he decides to take revenge, as well as to get his husband back.
Jungwoo eventually encounters Mark, a wealthy young man and Donghyuck's obsessive lover, studying in the same college as him. Mark offers Jungwoo to help him with the plan which Jungwoo avoids at first but goes ahead later on and they together proceed with their planning. However, things start unrolling in unexpected ways when Jungwoo and Mark start falling for each other and that's how the four souls start searching for their final destination which was already their predestination.