After Oh Laura loses her son, Nam Sin, to her father in law, Nam Gun Ho, she creates an AI robot that looks exactly like Nam Sin. Nam Sin grows up to as the heir of a rich conglomerate, PK group. He is infamous within the society for his reckless acts. However, he has no intentions of following his grandfather's footsteps and runs away.

Thrust into the world of his human counterpart, Nam Shin III shakes things up at PK Group and risks his facade. Kang So Bong chases justice when she finds out she was duped, but how will Nam Shin III deal with her when he's never met her before?

Young Hoon, Sin's personal secretary, follows Sin into Czech Republic. After seeing Nam Sin in a coma and Oh Laura taking care of him, Young Hoon feels shocked. Meanwhile, Gun Ho, the CEO of PK group, tries to fill in for Sin's presentation of their Driverless Car Project, but Mr. Seo gives the presentation instead.

So Bong barges into the presentation room and tries to argue with Nam Sin, but she fails. She tries to argue with him again at a club with Ms. Jo's help, but that is stopped too. However, a fire breaks out at the club. So Bong ends up stuck beneath collapsed debris, but Namsin helps her out.

So Bong's world is turned upside down when she realizes Nam Shin's personality isn't the only thing different about him. Chairman Nam comes up with a polarizing idea to help PK Group save face.

So Bong asks Namsin to take her in as his personal bodyguard, and Namsin decides to take her in. However, Namsin and Young Hoon are still suspicious about her, so they keep an eye out for her. Meanwhile, So Bong follows Young Hoon to PK hospital after hearing his conversation on the phone.

The potential scandal surrounding Chairman Nam's dementia reaches a boiling point. Ye Na decides to tighten the knot and proceed with her engagement despite her father's trouble.

Namsin makes So Bong think that she was mistaken. Meanwhile, the test driving of the driverless car is held in front of many reporters. However, as Sin and So Bong follow the driverless vehicle, they realize that something has gone terribly wrong.

In the wake of Kang So Bong's departure, Nam Shin III deals with unexpected errors in his perception and behavior. Meanwhile, his wedding day arrives, but Executive Director Seo has other plans.

Nam Shin III's face-off with Executive Director Seo's mysterious man comes to a dangerous conclusion. With Nam Shin III's growing free will, Professor Oh is pushed further to make the ultimate choice.

So Bong is shocked to be suddenly kissed by Namsin3. In the end, she realizes that Namsin had no bad intentions on this action and decides to continue helping him. However, Ye Na becomes jealous of this and tries to start living with Nam Sin's house. Meanwhile, So Bong tells Mr. Seo about Ye Na to get rid of her.

Jong Gil overhears Chairman Nam throwing a fit as his dementia kicks in, so he tries to confirm what he overheard. Young Hoon asks Ye Na to find out if Jong Gil is sure about what he had heard and tells Namsin. Meanwhile, Jong Gil tries to confirm what he heard by threatening Ho Yun with her child.

Namsin tells Chairman Nam that he doesn't have dementia. Jong Gil becomes sure that Chairman Nam has dementia and tells So Bong to stay silent about it. Meanwhile, Namsin finds out about Hee Dong's secret and offers a deal to Ho Yun. However, Namsin gets in trouble as he becomes unable to resupply his battery on time.

Everyone is surprised as Ye Na suddenly steps up and rushes getting married with Nam Sin. So Bong's father hears about this and visits PK Group out of anger. Meanwhile, So Bong feels uncomfortable as Ye Na keeps mistreating Namsin. This makes her step up to stop Ye Na from mistreating Namsin.

Shin's chaotic game of revenge runs on at Shin III's expense, who finds himself unable to fight back. Meanwhile, Seo Jong Gil lays the groundwork for his scheme, and brings Shin to a startling discovery.

After nearly being forced to cross the line, Shin III becomes unsure of the worth of his rules. On the other hand, Shin makes big strides against his grandfather, but even the trust of his allies cannot be certain.

Namsin starts to think and act on his own after So Bong leaves him. Laura becomes worried that Namsin's identity as a robot might get revealed as he starts to continue to show unexpected actions. This makes her meet So Bong herself. Meanwhile, Jong Gil's agent follows Laura and finds out that So Bong might be deeply involved with her.

So Bong just can't forget about Namsin after turning her back on him. She ends up visiting Laura's hideout to meet him. Namsin is very happy to see her again, but So Bong only tells him that he should do as Laura and Young Hoon tells him to do. Meanwhile, Jong Gil sends out his agent to find out what secrets So Bong holds.

Namsin leaves the wedding ceremony on his own to save So Bong. After saving So Bong, he chases after Jong Gil's agent. Laura become furious because Namsin keeps getting out of control. Meanwhile, Laura and Young Hoon are shocked to hear that Nam Sin isn't showing any progress and is becoming a lost case.

Jong Gil gets more and more suspicious about the true identity of Namsin. Namsin tries to know more about So Bong after becoming friends with her. Laura is troubled as Namsin gets completely out of her control. Meanwhile, something happens at the hideout while nobody is looking.

Laura is overwhelmed with joy as she finds out that Sin is getting better. However, she gets more nervous as Namsin continues to make decisions on his own. Ms. Jo tells So Bong that she has a video of Namsin breaking down a car with his bare hands and demands answers to her questions. Meanwhile, Laura tries to hide the truth about Sin getting better from So Bong and Namsin.

So Bong is upset to see Namsin continuing to listen to Laura without knowing that he has a kill switch installed in himself. Jong Gil finds where Ye Na is and tries to get into Laura's house. However, this causes Ye Na to panic and do whatever she can to keep Jong Gil away from Nam Sin.

So Bong confesses her love at the presentation, but unexpected events continue to occur. Nam Sin sees Laura after 20 years, but he acts coldly to her since he is angry about the very existence of Namsin3. Meanwhile, So Bong tries to negotiate with Laura to take away the kill switch from her.

After hearing So Bong's love confession, Namsin tries harder to understand and feel emotions. However, Sin is more frustrated after meeting Namsin and starts to wonder what Laura really thinks about Namsin. Meanwhile, So Bong's dad, Jae Shik, is shocked to realize that his daughter is in love with a robot.

Nam Sin becomes more and more angry as he gets rejected by So Bong and realizes how Laura really feels about Namsin. This makes him call Jong Gil to the hideout. Namsin and So Bong return to their daily lives. Meanwhile, Chairman Nam invites Namsin to discuss about when and how he will give him his position.

Nam Sin knows that everyone has done what they did for his own good, but he gets so angry that he says harsh things to Young Hoon. Chairman Nam offers his position to Young Hoon to see what he thinks, but Young Hoon's reply wasn't what he expected. Meanwhile, So Bong decides to never leave Namsin's side.

Nam Sin feels threatened by the robot Namsin and decides to go to work even if he hasn't fully recovered yet. So Bong continues to work as Nam Sin's bodyguard to protect Namsin. However, Nam Sin has his own reasons to go to work. He tries to find something without telling even Young Hoon about it.

Nam Sin becomes angrier as he continues to find Namsin's traces everywhere he goes. He tries to get rid of such traces and find a way to make Namsin get in trouble. Chairman Nam calls Namsin, and Namsin visits David after hearing shocking news. Meanwhile, Nam Sin overhears the conversation between Namsin and David.

Nam Sin becomes furious as he realizes that Chairman Nam has known that he had been replaced by a robot. His anger leads him to ask Laura if there would be any way for him to destroy Namsin. Laura tries to avoid the situation, but she ends up giving him access to the manual mode as he demands.

Jong Gil calls out Nam Sin by saying he has something to tell him. Another error occurs in Namsin's system, and he sees a hallucination of So Bong. This makes him unbearable to hold back anymore, so he goes to see So Bong. Meanwhile, Nam Sin tries to get back at Chairman Nam after hearing a recorded message from Jong Gil.

Nam Sin abuses the manual mode and makes Namsin attack Chairman Nam. However, things don't go as Sin has planned. Jong Gil overhears that Chairman Nam really does have dementia and tries to come up with another plan by pretending to help Nam Sin. Meanwhile, Young Hoon is furious that Nam Sin had tried to kill his own grandfather, and Laura becomes desperate as Nam Sin keeps going too far.

Nam Sin makes Chairman Nam sign the stock transfer agreement papers and becomes the new chairman of PK Group. However, Young Hoon suddenly returns to Nam Sin's side and blocks of Jong Gil. After returning, Young Hoon carefully sets up a plan to make things go back to where they belong. Meanwhile, Laura is invited to the company by Nam Sin.

Namsin3 reveals his identity at the company meeting. Everyone in the room is surprised, but they leave with satisfaction after hearing about his plans for M-City. Nam Sin becomes furious as he realizes that everyone including Young Hoon has tricked him and stabbed him in the back. Meanwhile, David tells So Bong that tomorrow is Namsin3's birthday.

So Bong prepares a surprise party for Namsin3. Jae Shik takes Namsin3 to a spa, and Namsin3 picks up his gift for So Bong. Nam Sin finds the kill switch and tries to destroy Namsin3, but Laura gets a call from Ye Na and tries to stop him. Meanwhile, Jong Gil finds out that Nam Sin, Namsin3, and Laura is heading to a construction site and follows them.

Namsin3 gets framed for murdering Laura and goes into hiding with So Bong. Nam Sin get heartbroken by hearing that his mother is dead. Ye Na's instincts tell her that something is suspicious about her father, Jong Gil, and tries to find out what it is. Meanwhile, Jong Gil visits the office and meets Young Hoon.

Namsin3 realizes that the kill switch has been reactivated and tells David about it. So Bong ends up finding out about this as well and tries to stop Namsin3, but Namsin3 insists that he must save Nam Sin. Meanwhile, everyone is out to search Namsin3 and Nam Sin, but Jong Gil refuses to give up so easily.