On a wedding anniversary night, Yeo Wool loses her husband. After one year, Yeo Wool puts everything behind and moves to an island to get her only son Yi Chan accepted in a prestigious school. She tries to settle in and get along with other parents there, but she encounters someone who she never wants to meet again on the school reception day.

Yi Chan’s classmates and their mothers completely isolate Yeo Wool and Yi Chan from their gatherings after what happened to him at school. Thankfully, Jae In and her mother reach out to them and spend time together. Meanwhile, Yeo Wool receives a suspicious parcel and a message from an unknown sender.

It’s time for the kids to decide on the school club they wish to join. Yeo Wool chooses to let Yi Chan join a hockey club. On the registration day, she encounters Ji Sun, Do Young, and the other moms. Meanwhile, Yeo Wool continues trying to find out the relationship between her dead husband and Do Young. She hires a private detective to dig into Do Young. Yeo Wool soon receives surprising news from the private detective.

Do Young tells Yeo Wool that she had no choice but to turn a blind eye to Yi Chan's incident because she was afraid to get caught having an affair. However, she’s not the one who locked the locker. Meanwhile, Yeo Wool volunteers to prepare snacks for Camp Day, and Ji Sun throws them away.

Jae In looks into Yi Chan's dad's cell phone and gets confused as she sees the photos of her family in there. While Yeo Wool is sleeping, Na Yoon finally reveals her true colors and tries to get rid of her. Meanwhile, Ji Sun plans to kick Yi Chan out of the school with other parents, but Yeo Wool finds out her weakness.

Yeo Wool and Na Yoon slowly drift apart after Yeo Wool notices that Na Yoon was stabbing her in the back. And Chef Jung tells Yeo Wool that Ji Yong was with another woman right before he went on a yacht with Yeo Wool on the night he died. Meanwhile, Jae In tells Yi Chan and their whole class that they are related.

Na Yoon sues Yeo Wool for trespassing and damaging her painting, and Yeo Wool meets the detective who was in charge of Ji Yong’s case at the police station. Soon Sang feels bad for Yeo Wool and decides to quit his job and leave. Meanwhile, Ji Sun is not happy with the rumor about Yi Chan and Jae In.

Yeo Wool receives a text message from Ms. Doh and goes down to her office. But when she gets there, she finds Ms. Doh lying down on the floor, unconscious. Yeo Wool quickly calls 911, but everyone suspects her because she was the first one to find Ms. Doh. Meanwhile, Na Yoon gives her statement to the police and takes Yi Chan with her.

Yeo Wool is arrested and questioned by the police as a suspect of murder. Yeo Wool quickly calls Soon Sang for help before they search her house. Then Yeo Wool warns Na Yoon for reporting a false statement. Meanwhile, the police find out who has turned off the circuit breaker at the school on the recital night.

On a rainy day, someone throws a rock and breaks the window of Yeo Wool’s house, and Danny comes to save Yeo Wool and Yi Chan. Meanwhile, Ae Soon is arrested for vandalism as she gets caught watching Yeo Wool in front of her house that night. Therefore, Yeo Wool sets up surveillance cameras at every corner of her house and notices something strange.

Soon Sang and Yeo Wool find a tunnel that leads to a secret room in her place. She gets shocked and furious to find out someone has been watching her home from the beginning. Soon Sang takes both Yeo Wool and Yi Chan to his place for the time being. Meanwhile, Na Yoon becomes the new foundation chairman and fires Yeo Wool.

Ji Yong is alive. Yeo Wool figures out he has been conspiring with Alex all along, and therefore, she suspects Na Yoon as well. Even though they hate each other, Yeo Wool tries to help her and warns her, but she does not believe in Yeo Wool. Meanwhile, Ji Sun is about to leave for vacation with her children but, she gets an urgent call.

Na Yoon is unconscious from the car accident, and Yeo Wool comes running to the hospital and meets Ae Soon. Yeo Wool starts to investigate this accident thoroughly as she suspects Ji Yong is the one who is responsible for it. Meanwhile, Ji Sun secretly goes into the woods in the middle of the night to hide something.

Even after Na Yoon’s death, Detective Gu still suspects Yeo Wool as she is Ji Yong’s wife. However, Detective Gu and Soon Sang work together to arrest Ji Yong through Yeo Wool. Meanwhile, when Yeo Wool voids the contract with Wan Chai Group on behalf of Na Yoon, Ji Yong finally calls her to meet her in person.

Ji Yong threatens Yeo Wool to replace the money on Na Yoon’s account, and he tries to kill her on the yacht. Now that the truth comes out about Ji Yong being alive all along, Detective Gu apologizes to Yeo Wool for suspecting her. Meanwhile, Ji Sun manages to get Jung Woo out of the police station in Seoul, but another trouble is waiting for her in Jeju.