Twenty-five years ago, a government funded experiment sought to isolate the genetic marker for psychopathic tendencies by testing unborn children.  Now, a chain of serial killings is striking fear in the hearts of the nation and the cases seem to link back to the original experiments.  A young, caring police officer and a veteran detective are determined to solve the cases and arrest the killer, but the murders may have more of  a personal effect on them than they ever imagined.

Lee Hee Joon as Ko Moo Chi

As a young boy, Ko Moo Chi's entire family was killed by the serial killer, Han Seo Jun.  Now, as a detective, a copy-cat has surfaced and is terrorizing the city.  Moo Chi is determined to find the killer and inflict judgement however he can.  But when the killer suddenly turns up dead, something still seems off.  And the more he learns, the more complicated things seem to get.  When all the signs start to point to the police officer who has been helping him on the case, he really hopes that he is wrong.  

Ko Moo Chi is hot-headed and reckless.  He has lived his whole life with the guilt of knowing that his parents died trying to give him his birthday wish and his brother ended up disabled trying to save him.  His anger and resentment make him a determined detective with a chip on his shoulder.  I liked Lee Hee Joon in this role.  His strong sense of justice was relatable and well played and he and Lee Seung Gi made a great team.  From friends to enemies, their energy was dynamic and interesting.

Park Joo Hyun as Oh Bong Yi

Oh Bong Yi is a young girl from Ba Reum's neighborhood.  She has a crush on him and he has identified her as someone who would be easy to control, even if she found out the truth about him.  But after his surgery, Ba Reum ends up really falling in love with her.  Unfortunately, once he realizes that he was the one to kill her beloved grandmother, he knows that she will end up hurt no matter what he does.

♥ Child Actors

The child actors in this drama were required to do some seriously heavy lifting and they all did an amazing job.  These roles required a maturity of emotion that must have been challenging and difficult for children so young.  I have so much respect for their acting ability and hope we will get to watch them in many more roles to come.   

♥ Flawed Lead

"Mouse" took a unique approach by giving us a flawed lead who gave us his unreliable account of events for the first half of the drama.  And it is an amazing testament to Lee Seung Gi's acting skills that even after finding out what a monster he was in the beginning, I was still broken hearted to see him die in the end.  This is not a handsome hero story but it is a story of the kind of redemption and grace that can come to even the most flawed of humans.  

Oz

I just didn't really think the whole OZ storyline was necessary.  The story was full enough and they could have easily left it with Doctor Daniel and Han Seo Jun's experiments.  The members of OZ didn't contribute that much to the overall plot and I didn't find their portion of the story that interesting.  In a drama already packed with characters and themes, I feel like this one could have been left out and no one would have missed much.  

Psychopaths

I know this is just a drama, not a documentary, and fiction can either simplify or stretch the truth as it sees fit, but I didn't like the way this drama represented psychopaths.  First, not all murderers are psychopaths, so ridding the world of babies with that gene does not magically create a safe existence free from crime and killing.  And second, not all psychopaths kill people.  There are enough misconceptions about these kinds of mental illnesses and I feel like we should be careful about over-generalizing.  

As expected for a drama so dark, there isn't much happily ever after in this one, although they do a fairly good job of trying to tie up all those crazy loose ends.  This is a long one, so hold onto your seats.  In the end, all the members of OZ, plus their fearless leader, Choi Young Shin are arrested for their crimes.  So are Ba Reum and Hong Joo.  With those arrests, Yo Han's name is finally officially cleared of any wrong-doing.  6 months later, Ba Reum is suffering terrible physical pain because of his brain surgery and emotional pain, now that he remembers all the crimes he has committed.  In a final act of revenge, he kills Han Seo Jun for Moo Chi.  His final scene is a vision of him and his younger self in a church.  He tells the child that his prayers have been answered and he is no longer a monster.  Then Ba Reum bows his head and dies.  Three years later, Choi Young Shin receives a pardon from the Blue House and is set free, but she is killed on the drive back into the city.  Hong Joo's parents have been raising her son while she served her time, but now she is finally free.  Moo Chi has left the department to sell eggs and support Bong Yi while she goes to college.  He goes to put a marker on Ba Reum's grave behind the prison, so he seems to have finally made his peace.  The series ends with a dinner party at Bong Yi's house that tries to add some levity to the final moments, but seems surprisingly superficial and heavy.  We do get a short scene where Moo Chi and Hong Joo talk and he apologizes for his part in wrongly accusing Yo Han.  After the credits we get two bonus scenes.  One shows the mouse from Han Seo Jun's original experiment miraculously coming back alive.  And the other shows a new doctor performing a brain transplant, so apparently this research didn't die with Han Seo Jun after all.  While these scenes could open the door for a season two, I suspect they are just a reminder that corruption and evil still live on.