This drama is not about the normal type of story as you see in any other drama. On the contrary, it is about chasing a serial killer and the ability to retrieve the dead. However, there is a complicated twist to this ability. A deceased person might transfer, after being retrieved, to a different body, forcing you to live someone else's life. And of course, Abyss should not be called a Korean drama if it does not include some romantic stuff.
Although the storyline was pretty good and the chemistry between the characters was fine, something was missing that kept me fast-forwarding episodes several times.
It might have something to do with the first episode in which the producers already revealed the two suspects. For someone like me it's then quite difficult to pay attention to the story. Watching the characters searching the suspects for 16 episodes when you already know the answers is not much fun. Actually, you should call it boring.