Ha Won runs a company called AH and is an AI programmer. His latest project is a conversation device with his own personality programmed into it. Ha Won wanders into a recording studio where he meets sound engineer Seo Woo. After their meeting, Ha Won’s device finally starts working. Meanwhile, Seo Woo gets a weird request from her new boss.

Seo Woo blames herself for meddling in Ha Won and Ji Soo’s complicated relationship and causing Ji Soo pain, but she can’t help but grow more curious about Ha Won. She ends up telling the man she calls Before Dawn about this situation. Meanwhile, Ha Won and Ji Soo speak to each other on the phone for the first time in seven years and plan to meet up.

Seo Woo has a tough time after Ji Soo’s accident in Norway. However, she finds herself worrying about Ha Won more than herself and is caught off guard by these emotions. Ha Won wants to know more about Ji Soo through Seo Woo. As they continue to meet, Seo Woo discovers another one of Ha Won’s secrets.

Ha Won still wants to know what the point of reaction was for Ji Soo’s conversation device. As Seo Woo continues to help bridge the gap between Ha Won and Ji Soo’s character within the device, the two become closer to each other. Meanwhile, In Wook goes through a slump after Ji Soo’s death and keeps bumping into Soon Ho.

Seo Woo’s feelings for Ha Won are now out in the open. Seo Woo is quite embarrassed by this, but she continues to help Ha Won get closer to Ji Soo. Finally, Ji Soo agrees to have a conversation with Ha Won. However, Seo Woo figures out that Ji Soo will eventually remember what made her miserable and wants Ha Won to stop.

Ha Won is determined to stop liking Ji Soo. Seo Woo tries to stop having feelings for Ha Won as well, but Before Dawn keeps showing up at the recording studio. Meanwhile, In Wook finds out who the phone number Ji Soo had written down belongs to. His flippant attitude and sudden changes in mood annoy Soon Ho.

Ha Won is determined to stop liking Ji Soo. Seo Woo tries to stop having feelings for Ha Won as well, but Before Dawn keeps showing up at the recording studio. Meanwhile, In Wook finds out who the phone number Ji Soo had written down belongs to. His flippant attitude and sudden changes in mood annoy Soon Ho.

Seo Woo feels that her one-sided love is slowly growing into something more than that. However, Seo Woo keeps thinking of reasons why she shouldn’t let her emotions go on any further. Meanwhile, Min Jung, the newest resident of Eunjoo Homestay, has a break-through in a therapy session with Ha Won’s device.

The day of In Wook’s recital approaches and he is grateful to Soon Ho for bringing him out of his slump. However, Ha Won realizes that In Wook is Ji Soo’s husband who is connected to his mother’s death. Ha Won wants to meet In Wook and In Wook also wants to see the house that belongs to the shipping address.

Ha Won confronts In Wook at his recital and finally learns the truth about his mother’s death. Seo Woo tries hard to help Ha Won recover from the confusion and pain. Feeling betrayed, Ha Won refuses to take Soon Ho’s calls. Meanwhile, In Wook runs into someone at the recording studio and figures out the relationship between Seo Woo and Ji Soo.

Seo Woo tells Ha Won that she needs some time apart. Ji Soo’s personality within the device figures out what happened to her in real life and asks Seo Woo for a difficult favor. Ha Won also works up the courage to return to the place where he experienced so much pain. Each person finds their own bit of strength to go on.