Due to a mysterious conspiracy, a man and a woman, who took part in a 24 hour freezing project, wake up 20 years later, instead of 24 hours later. In order to survive, the man and the woman have to keep their average core body temperature at 31.5°C. Their relationship develop romantically. Once out of the freeze, the two experience a dangerous side effect from the project wherein they must maintain a core body temperature of 31.5 degrees Celsius (approximately 88.7 degrees Fahrenheit) to survive. Coupled with the warming of their hearts from romantic attraction, they find themselves in a sticky situation.
Professor Hwang goes missing, and there is no other way to defrost Dong Chan and Mi Ran. The station covers up about the experiment and the shoot to hide its fault. 20 years later, Dong Chan and Mi Ran wake up due to a malfunction of the machine. They look for their families and find out that 20 years have passed.
Dong Chan and Mi Ran get to reunite with their family members 20 years after they participated in the cryonics experiment. They’re shocked by the fact that it’s the year 2019 now. They also have a hard time dealing with how the world has changed. Meanwhile, Ha Young goes to a cafe to meet someone.
After Dong Chan announces that he participated in the cryonics experiment on the TV news program, he becomes the talk of the town. People start to recognize him wherever he goes. Some argue that there was another woman who took part in the experiment with him. Meanwhile, Byung Sim tells Mi Ran that he still loves her, and Mi Ran gives him a good beating.
Mi Ran asks the broadcasting station for compensation for the 20 years she has lost. She demands an astronomical amount of money. That makes Hyun Gi and Hong Suk go panic. Byung Sim’s heart pounds every time he runs into Mi Ran. Meanwhile, an article about Dong Chan is released, and people at the broadcasting station start to gossip about him.
Professor Hwang’s assistant Professor Jo’s car explodes right after he gets out of the car. The police open an investigation to find out who is behind the explosion. Ha Young also decides to cover the explosion on her news program. Meanwhile, Dong Chan and Mi Ran are lost on the mountain, but their temperature starts to rise as they walk.
Mi Ran apologizes Dong Chan for kissing him on the mountain, but that only makes Dong Chan feel confused. Mi Ran is reunited with Yu Ja who used to be a shaman. Yu Ja tells Mi Ran that she’s meant to be Dong Chan. Mi Ran realizes that she is being swayed by Dong Chan. Meanwhile, Byung Sim decides to be a neighbor of Mi Ran and her family.
Mi Ran deals with the online post about the exposure of her involvement in the cryonics experiment, and people start to support her. She continues to work as an intern at the broadcasting station. Meanwhile, Professor Hwang regains his memories and goes to his lab. However, he is abducted and threatened by Hyeong Du.
Mi Ran is confused by how Dong Chan acts. He looks like he sometimes makes a step towards her, then suddenly he pushes her away. And a rumor about Dong Chan is spread in the broadcasting station. Meanwhile, someone uploads a post online about Mi Ran’s participation in the cryonics experiment 20 years ago.
Dong Chan offers Mi Ran an internship at the broadcasting station, and Mi Ran accepts it. Dong Chan tells her to make proposals for variety shows. Hong Suk asks Dong Chan to make an appearance on a TV news program. Meanwhile, two thugs tail and threaten Dong Chan. In the end, they even abduct Dong Chan and Mi Ran.
Mi Ran and Dong Chan still need some time even after they share a kiss. Dong Chan just wants Mi Ran to be happy and worry-free. Meanwhile, Ha Young threatens Hyeong Du, saying that she knows he is a fake. Hyeong Du is flustered and in turn, goes to threaten Professor Hwang. Finally, Dong Chan collapses from an unknown illness.
Dong Chan moves into Mi Ran’s house while waiting for her to wake up. Three years have passed, and Ha Young comes back to Korea. The result of the clinical trial is a success, and they decide to perform surgery on Mi Ran. However, the situation seems to be difficult for her to wake up.
In 1999, a star director Ma Dong Chan is on a roll. He is renowned for trying new things and making sensational variety shows. He volunteers to participate in cryonics experiment with Ko Mi Ran who has done various experiments with him. Meanwhile, the doctor in charge of the experiment leaves before the subjects thaws.
Dong Chan comes to visit Hyeong Du and offers a deal that they exchange Professor Hwang and Seok Du. Professor Jo continues trying to find the antidote for Mi Ran and Dong Chan. And finally, the pilot episode of “Go Go 99” airs. Everyone involved in the show watches the show together, but they are shocked at the opening of the show.
Terry tries to attack Mi Ran, but she counterattacks him. Hong Suk tells Ha Young that she should go to Washington as a correspondent. Dong Chan’s body temperature comes back to normal, and it is Mi Ran’s turn to get the injection. However, Mi Ran gets stabbed while protecting Dong Chan.
Dong Chan tells Hyun Gi and Hong Suk that they should tell the prosecution the truth to avoid getting humiliated later. Hyeong Du insists that he is the real Seok Du at the temporary board meeting, but the real Seok Du appears. Meanwhile, Dong Chan submits his resignation letter.
Mi Ran sees Dong Chan and Ha Young hugging and thinks he still has feelings for Ha Young. Meanwhile, Dong Chan and Mi Ran still get tensed up since Terry Kim has not been arrested. Ha Young saves Mi Ran from an accident, while Mi Ran learns the shocking truth about Ha Young.