In the year 2007, before the main events of the drama, 11-year-old fraternal twin brothers Kim Woo-jin (Jung Ji-hoon) and Kim Bum-gyun (Kim Ye-joon), along with their neuroscientist father Dr. Kim Kyu-chul (Kim Joong-ki), witness the arrival of a female humanoid alien (Gong Seung-yeon). Out of pity and curiosity, the family brings the alien with them and adopts her as a member of the family. The twins become fond of her, especially Woo-jin who names her Byul.[a] By chance, Dr. Kim discovers Byul's secret: she had brought with her an advanced form of technology that can record, and even lock, memories and convert them into video. In order to closely study this alien technology, Dr. Kim isolates himself from his family to work secretly on Byul in what he calls the "Beta Project." Dr. Kim never goes back home, making the twin Bum-gyun think Byul has taken their father captive, though Woo-jin believes their father has abandoned them.
In 2017, Woo-jin (Yeo Jin-goo), now a 21-year-old college student in neuroscience, feels that a series of suicides in his university is somehow linked to Bum-gyun (Ahn Woo-yeon), who has been searching for aliens, particularly Byul. While in pursuit of the case, Woo-jin meets Han Jung-yeon (Gong Seung-yeon), a computer science student who, to his great shock, looks very much like Byul. She is also investigating the multiple suicides, all of which she thinks are actually murder.
In 2037, South Korea is now divided into Normal Earth,[b] a heavily polluted place where crimes are rampant, and Smart Earth,[c] a clean, peaceful, and crime-free city. Kim Joon-hyuk (Kim Kang-woo) is a Normal Earth crimes detective who tries to get into Smart Earth to investigate a case of twin brothers who went missing in 2017. In doing so, he starts to uncover the dark truth lurking behind Smart Earth being “crime-free.”
Each episode of the drama, except the last, contains two parts: Part 1: Beta Project,[d] which contains a plot set in 2017, and Part 2: A Great New World,[e] which contains a plot set in 2037. The two plots merge in the twelfth and final episode of the series, titled Circle: One World.[f]
a 21-year-old second-year university student in the Department of Neuroscience in Handam University of Science and Technology in the year 2017; Bum-gyun/Joon-hyuk's "younger" twin brother and son of Dr. Kim Kyu-chul
In his younger years, Woo-jin was an enthusiast about UFOs and extraterrestrial life. He witnessed (with Bum-gyun and Dr. Kim) the arrival on Earth of a female humanoid alien, which he names "Byul." His passion faded when his father disappeared with Byul. In 2017, he meets Byul (now Han Jung-yeon) once again and together they investigate the serial suicides in the university, with the help of Detective Hong Jin-hong.
Kim Kang-woo as Kim Joon-hyuk (future and amnesia's Kim Bum-gyun)[3]
(A Great New World) a 41-year-old violent crimes detective from Normal Earth in the year 2037; Woo-jin's "elder" twin brother and son of Dr. Kim Kyu-chul
Joon-hyuk enters Smart Earth to investigate cases happening within the supposedly "crime-free" city, with the help of Detective Hong Jin-hong and the alien hacker Jung-yeon a.k.a. Bluebird. Twenty years before (as Kim Bum-gyun) he was consumed with aliens on earth and had in facat been in a psychiatric hospital and prison for his seemingly mad behaviours. By 2017, he is investigating the series of suicide in Handam University of Science and Technology that he believed were brought about by aliens. He loses his memories later on; Detective Hong gives him his new name "Joon-hyuk" and he enters the police force.
During her arrival in 2007, Byul appeared naked to the Kims and was also mute, having no knowledge of any human language. She becomes close to Woo-jin, who gave her the name "Byul," and she learns how to speak Korean. She is a semi-immortal being, i.e. she never ages and will look the same as long as she lives. She had brought with her an advanced form of alien technology that can record, and even lock, memories and convert them into video. She was taken for scientific research by the twins' neuroscientist father and later loses her memories. She is adopted by Professor Han Yong-woo who named her Han Jung-yeon.
(A Great New World) an intelligent 26-year-old government employee in Smart Earth in the year 2037
Ho-soo is unbelieving at first on the possibility of criminality in Smart Earth and sides with the government. He is tasked to keep watch on Joon-hyuk who is investigating cases in the "crime-free" city. Upon learning the truth from Joon-hyuk, he becomes confused, but later sides with Joon-hyuk and Bluebird to take down the unjust powers controlling Smart Earth.
a 21-year-old medical student who fell in love with Bum-gyun in 2017. She helped Bum-gyun, Woo-jin, Jung-yeon, and Detective Hong Jin-hong in investigating the serial suicides in the university.
He is a police detective who began investigating the serial suicides in Handam University of Science and Technology, along with Woo-jin, Jung-yeon, and Min-young. He becomes suspended due to his involvement with the case.
He is the father of the twins Kim Woo-jin and Kim Bum-gyun (Kim Joon-hyuk). He is a neuroscientist specializing in treating trauma, working together with fellow neuroscientist Han Yong-woo, taking advantage of Byul's special memory-controlling technology.
He is a professor and the dean of the Department of Neuroscience in Handam University of Science and Technology. He once worked together with Dr. Kim Kyu-chul in treating traumas using Byul's special technology. He became Byul's father a year after she came on Earth.
In 2037, she has become a skilled doctor and Joon-hyuk/Bum-gyun's girlfriend. She would always help him during investigations, especially in times when her expertise is needed.
In the table above, the blue numbers represent the lowest ratings and the red numbers represent the highest ratings.
This series aired on a cable channel/pay TV which normally has a relatively smaller audience compared to free-to-air TV/public broadcasters (KBS, SBS, MBC and EBS).
