Lost

Lee Boo Jung is a forty-year-old home manager living a cold and hopeless life. She receives a summon letter from the police when someone sues her for cyber-bullying. This confuses and shocks her husband whom she is estranged from. Lee Kang Jae is a twenty-seven-year-old young man who runs his own stand-in escort business. He has been chasing after a friend who borrowed money from him then disappeared. He then recieves news that the friend has been found dead in a lake.

Kang Jae and Ttak Yi hold a small funeral ceremony for their friend. Boo Jung visits the police station amongst protests of harsher punishment for cyberbullying. Her mother-in-law finds out the reason for the police summons and in a panic consults Boo Jung's father. Boo Jung is preoccupied with thoughts of her strange encounter on the bus.

An upset Boo Jung once again runs into Kang Jae, this time on the rooftop. Kang Jae calms her down and tells her they should exchange number the next time they meet. Jung Soo and Kyung Eun reconnect. Kang Jae is offered a scam job by Jong Hoo.

Ttak Yi and Min Jung worry if Kang Jae has gotten himself mixed into something troublesome. Kang Jae's twenty-seventh birthday arrives. Everyone ends up in the same wedding ceremony complex. Ttak Yi runs into his sister who thought he was at the library. Boo Jung is summoned to work when an expensive handbag goes missing.

Kang Jae gets dragged deeper into the shared past between Jung Woo and Lee Boo Jung when he visits Jung Woo's old place and finds his phone. After an anonymous account posts rumors about Jung Ah Ran's past, Boo Jung is encouraged to reach out to an old acquaintance. Boo Jung's mother-in-law and father find out about the truth.

Kyung Eun reaches out to Sung Joo and they spend the evening reminiscing about the past. Boo Jung and Kang Jae meet per their arrangement. They talk while sharing tangerines, simply keeping each other company. Despite Jong Hoon's enthusiasm to hear about Kang Jae's success with his target, Kang Jae offers him nothing in return.

After a scare at the hospital, Kyung Eun and Jung Soo have dinner together and she shares her fears with him. Boo Jung and Kang Jae once again meet on the rooftop and Boo Jung tells him about her miscarriage. Min Jung tells Ttak Yi the story of David, Uriah, and Bathsheba.

Woo Nam's ex-wife shows up at Soon Gyu's pharmacy. Boo Jung goes for a check-up, a year after the incident which triggers bad memories for her. Jung Soo decides to surprise Boo Jung at work and brings her macarons.

Kang Jae has dinner at his parents' place. Boo Jung worries about her father's escalating dementia. Jong Hoon confronts Kang Jae with the photos he has of him and Boo Jung and threatens him to stop meeting with her. Kang Jae reluctantly accepts. Spring slowly takes over winter.

Min Jung and Ttak Yi stay at Kang Jae's place. Jung Soo attends the funeral ceremony for Kyung Eun's husband. When Kang Jae arrives to sign Boo Jung out of police custody, the two end up stranded out of town and spend the night wondering about before deciding on an unlikely destination.

After spending all night walking around, Boo Jung and Kang Jae watch the sun rise together before making their way down the mountain to head towards the sea. Ttak Yi and Min Jung spend an equally sleepless night hunting for blankets around Seoul.

Kang Jae and Boo Jung reluctantly part ways as Boo Jung returns to Seoul and Kang Jae heads to the seaside. Bong Min Ja and Lee Chang Sook have lunch together and talk about their past. Ji Na is admitted to the hospital due to severe injuries.

Boo Jung and Ah Ran run into each other at the hospital when she and her husband try to silence the actress and make the assault allegations go away. Kyung Eun and Jung Soo meet again and spend the night together. Ah Ran shows the photos to Boo Jung, leading her to make a decision about her relationship with Kang Jae.

Lee Boo Jung and Jin Jung Soo both find themselves in situations that test the strength of their marriage. Meanwhile, Lee Chang Sook gets lost in an unfamiliar part of the city.

Finally ready to accept her place in the world and coming to terms with death as a part of life, Boo Jung steps foot onto a new path in life to forge her future as she wishes. Kang Jae decides to move on from the darkness of the past by finally returning Jun Woo's possessions to his family and permanently cutting ties with Jong Hoon. Spring slowly warms into summer.