"Abyss" basically tells the love story between Cha Min and Goo Se Yeon.

They have known each other since they were little and their friendship lasted until adulthood. Cha Min has a crush on Se Yeon, but she only likes him as a friend. He works for her mother's company and Se Yeon is a prosecutor. One day, Cha Min is on the edge of a building and a strange thing happens, some "aliens" accidentally let him fall and he dies, so they bring him back using a glowing ball called "Abyss". The problem is that he comes back with a completely different appearance, becoming a handsome man.

Se Yeon is investigating a series of murders and unfortunately, she becomes the last victim. Cha Min is devastated by her death and brings her back to life using the abyss, she is then alive again, looking exactly like her least favorite person in the world: Lee Mi Do. The two join forces to find Se Yeon's killer and stop him from claiming more victims.

The romance between Cha Min and Se Yeon is too childish for me, I didn't really care about them and honestly, I never believed that Se Yeon liked Cha Min before his change, if she really liked him in these 20 years, wouldn't she have confessed already? Her excuse just didn't get me.

This is one of the things I really don't understand about this drama, the changes in appearance after being brought back to life. Cha Min makes some sense, thinking he was a good person and his soul looked beautiful, but how does it make sense that Se Yeon looks like a real person and even someone from her life? What would happen if Mi Do didn't have plastic surgery? Would two people with the same face exist at the same time, not being twins? And in the end, how is it that Se Yeon is living with Mi Do's face but using his real name? Ji Wook was arrested for his murder, how is that possible?

And the whole thing about abyss, we finished watching without really understanding what that thing is. How are so many people who died still alive? Cha Min and Se Yeon were brought back twice and there's also Hee Jin, Ji Wook, Oh Yeong Cheol and others... aren't there consequences to using this? It's almost become a normal thing to die and come back, it's so weird. You can say that Cha Min paid the price for disappearing for 3 years, but the right thing to do would be for him to come back to the way he was before the abyss, it would make more sense and what was that about the abyss disappearing because Se Yeon is pregnant?

The drama isn't bad, but the story is weak, as is the couple. There are some funny moments, which make it worth watching, but it's not something I would recommend.