Season 1

Soo Jin is quite a cold-hearted woman who studies birds, which are her only interested. She doesn't like children, but she has to work as an elementary teacher for a few weeks. A girl named Hye Na in her class catches Soo Jin's attention, and she starts to worry about her because the child doesn't seem to be taken good care of by her family. Before Soo Jin quits the school, she goes to Hye Na's house to say goodbye, but she is terrified to see something shocking there.

Hye Na goes missing at a port, and her backpack and shoe are found near it. Soo Jin takes a bus with Hye Na to go somewhere else, and Seol Ak thinks he saw a girl that looks like Hye Na in the street. Soo Jin happens to stay in a guest house and tries to get a fake passport for Hye Na, but something goes wrong and Soo Jin feels frustrated. Meanwhile, Jae Beom keeps looking for Soo Jin as Young Sin asked, but he only finds out that she already left.

Chang Geun starts to interrogate Ja Young after going through the surveillance camera footage. Soo Jin and Hye Na go to an orphanage where Soo Jin used to live when she was a child, but they are taken aback when they get there. Hye Na keeps staring at Ja Young and cries when she is on TV, so Soo Jin tells her that she can go back to her mom if she wants to. The detective finds out that Hye Na liked birds and tries to reach Soo Jin.

Soo Jin and Young Sin finally reunite in 10 years. Soo Jin asks for money without telling her mother about Hye Na, and Young Sin agrees to give her money on a condition. Hye Na goes to a barbershop woman whenever Soo Jin is away to meet Young Sin. Meanwhile, the police is still searching for Hye Na and Ja Young is arrested for child abuse.

Seol Ak runs away from the police, and he decides to chase after Soo Jin with the evidence he gets by chance. Young Sin finally receives cancer treatment. However, Soo Jin is determined to leave Korea with Hye Na. Meanwhile, Hye Na is getting closer with Hong Hee while she spends most of her time at the barbershop, and Hong Hee's mysterious past is about to be revealed.

With nowhere else to go, Soo Jin takes Hye Na to stay with Dr. Jeong for the time being. As Dr. Jeong sutures up her cut hand, Soo Jin tells him about her past. The next day, Soo Jin goes to confront her biological mom and asks her why she had abandoned her. While Hye Na waits for her at the playground, Hye Na coincidentally meets Hyun Jin, Soo Jin's sister.

Young Sin finds out about Soo Jin's biological mother, and she loses it. She is taken to the hospital as she passes out. Soo Jin has to introduce everyone to Yoon Bok. Young Sin asks Jae Beom to take care of Soo Jin's biological mother. She is also eager to survive after meeting Yoon Bok.

Hyun Jin finds out that Soo Jin kidnapped Yoon Bok. She blames Soo Jin for not thinking about her family and Ja Young. Seol Ak gathers clues at Jungaewon, and Ja Young goes to Young Sin's place. Yi Jin finds out Soo Jin didn't give birth to Yoon Bok. Meanwhile, Hong Hee tells Soo Jin about the day she left her.

Ja Young tries to take Hye Na back home, but Hye Na refuses to go back with her. Soo Jin also tells Ja Young to give up on Hye Na. Meanwhile, Young Sin says that she will break off the relationship with Soo Jin if she chooses not to return Hye Na to her biological mother.

Hye Na goes back to her spot to protect Soo Jin. Soo Jin goes around looking for Hye Na, but Seol Ak gets to find Hye Na first. Meanwhile, Ja Young asks for a public investigation to revenge Soo Jin. Soo Jin and Hye Na get reported as wanted. Young Sin and Hong Hee, the two mothers try their best to help Soo Jin.

Seol Ak kidnaps Hye Na and tells Ja Young to demand a ransom from Soo Jin. Young Sin becomes frantic by getting a call from Ja Young and rushes to prepare the ransom. Soo Jin chases after Hye Na with Jin Hong's help. Meanwhile, Chang Geun and Kyung Seok get nearer to Soo Jin.

Soo Jin and Jin Hong chase Seol Ak to Jungaewon. Chang Geun and Kyung Seok arrive at Jungaewon shortly after Soo Jin and Jin Hong move in to save Hye Na. Ja Young receives a text from Seol Ak. Meanwhile, Hye Na's kidnapping case goes public on the news.

Soo Jin and Hye Na go to Nami Island. They come across a father and son, Woon Jae and Woo Gyoon. Soo Jin gets worried as she sees that police are searching everywhere to find her and Hye Na. However, Soo Jin decides that it's time for her to decide and asks Hye Na's opinion.

Soo Jin and Hye Na get caught by the police. Soo Jin is taken to court while Hye Na is taken to an orphanage. During Ja Young's trial, Ja Young tries to get away by claiming that she didn't know anything about what Seol Ak did. However, the tide of the trial changes as Hye Na speaks in court.

Young Sin gets discharged from the hospital. She says that she wants to spend her last moments at home and reveals her secrets to each of her daughters. Yi Jin and Hyun Jin are surprised to hear their secrets. Meanwhile, Soo Jin suddenly hears the doorbell ring.

Tears flow as Cha Young Sin's family say their final goodbyes to their mother. After Young Sin's passing, Soo Jin takes Hye Na to Mooryeong Children's Shelter but promises her that one day they will be together again. In a quest to be reunited again, Soo Jin does whatever it takes to become Hye Na's legal guardian.