In 2009, Adrian Helmsley, an American geologist, visits astrophysicist Dr. Satnam Tsurutani in India and learns that neutrinos from a massive solar flare are causing the temperature of the Earth's core to rapidly increase. Arriving at a party in Washington D.C., Helmsley presents his info to White House Chief of Staff Carl Anheuser who takes him to meet the President. In 2010, U.S. President Thomas Wilson and other international leaders begin a secret project to ensure humanity's survival. More than 400,000 people are chosen to board enormous "arks" constructed at Cho Ming, Tibet, in the southwest Chinese Himalayas. A Buddhist monk named Nima is evacuated while his brother Tenzin joins the Ark project. Additional funding is raised by selling tickets for €1 billion per person. By 2011, valuable items are moved to the arks with the help of art expert and First Daughter Dr. Laura Wilson. In 2012, Jackson Curtis is a science fiction writer in Los Angeles who works as a limousine driver for Russian billionaire Yuri Karpov. Jackson's ex-wife Kate, and their children Noah and Lilly, live with Kate's boyfriend, plastic surgeon Gordon Silberman. Jackson takes Noah and Lilly camping in Yellowstone National Park. After an encounter with Helmsley, they meet Charlie Frost, who hosts a radio show from the park. Charlie plays a video of Charles Hapgood's theory that polar shifts and the Mesoamerican Long Count Calendar predict that the 2012 phenomenon will occur. Charlie also tells Jackson that those who discovered this and plotted to inform the public were killed in various accidents. After an earthquake hits Los Angeles, the family returns home. Jackson grows suspicious and rents a Cessna 340 to rescue his family. He collects his family and Gordon as Earth crust displacement begins with a magnitude 10.9 earthquake, and they narrowly escape Los Angeles as California collapses into the Pacific Ocean. As millions of people die in earthquakes worldwide, the group flies to Yellowstone to retrieve a map from Charlie, escaping as the Yellowstone Caldera erupts. Charlie stays behind to broadcast the eruption and is killed. Learning that the arks are in China, the group lands in Las Vegas to find a larger plane. They find Yuri, his twin sons Alec and Oleg, girlfriend Tamara and pilot Sasha. Helmsley, Anheuser, and Laura Wilson are aboard Air Force One where they are heading to the arks. President Wilson remains in Washington D.C. to address the nation one last time. With the Vice President dead and the Speaker of the House missing, Anheuser appoints himself Acting Commander in Chief even though he is not in the presidential line of succession. Back in Las Vegas, the group steals an Antonov An-500 aircraft and they depart for China as the Yellowstone ash cloud engulfs the city. President Wilson is later killed by a megatsunami that sends the aircraft carrier USS John F. Kennedy crashing into the White House. When the group arrive in China, the plane runs out of fuel and crashes into a glacier, killing Sasha, while the others make a narrow escape. They are then spotted by helicopters from the Chinese army. Yuri and his sons, possessing tickets, are taken to the arks, leaving the Curtis family and Gordon behind along with Tamara because Yuri knows she had an affair with Sasha. The remaining group are picked up by Nima and taken to the arks with her grandparents. They stow away on Ark 4, where the United States contingent is aboard, with the help of Tenzin. As a megatsunami approaches the site, an impact driver becomes lodged in the gears of the ark's hydraulic doors, preventing a boarding gate from closing, which in turn prevents the ship from starting its engines. In the ensuing chaos, Yuri, Gordon and Tamara are killed, and Ark 4 is set adrift. Jackson and Noah dislodge the impact driver and the crew regains control of the ark before it collides with Mount Everest. Jackson rejoins with his family, and he and Kate reconcile. As flood waters from the tsunamis slowly recede, the arks travel to the Cape of Good Hope in South Africa. Helmsley starts a relationship with Laura.?

Twelve-year-old Ann Uekusa and her mother move to the small town of Shimane, where Ann's grandparents live and everyone seems to be familiar with everyone else. Ann soon becomes friends with Daigo, a young boy who lives in Shimane, as well as Fuji and Shika, Fuji's younger sister and her best friend in Shimane. When Ann's mother, Miwako, commits suicide, Daigo helps Ann cope with the sudden change in her life. They fall in love, but Ann's life can only become more complicated when her estranged father suddenly arrives from Tokyo. After greatly contemplating going to Tokyo to live with her father after he asks her, she decides to stay. Ann tells Daigo about her decision but makes her go anyway. Ann and Fuji both live in Tokyo but hardly ever talk because Fuji goes to an elite high school, K High. Ann met back up with her friends she had before moving to Shimane and they continue their friendships. In Tokyo, she ends up becoming closer to Fuji, which causes conflict between her and Daigo.In Shimane, Shika learns the truth about her parentage and in her confusion, she begins to fall in love with Daigo. When Ann returns to Shimane, Shika upsets Ann's fragile emotional state so that Ann and Daigo will break up. In the end, Ann breaks up with Daigo for fear that her own sadness will weigh him down. Ann returns to Tokyo and starts a relationship with Fuji; however, because she does not love him, the relationship does not last. Daigo refuses Shika and rumors begin to circulate that he is interested in his middle school classmate Ayumu, who has been helping him studying to get into university and become a teacher.Nearing graduation, Ann learns that her father and his friend Kaede Kuroki have been dating and she is pregnant with Ann's half-sister. Ann's father and Kaede marry after being encouraged by Ann and Ann's grandmother. Fuji, now aware that Shika was the child of his mother's affair rather than himself, supports her decision to studying abroad in Vancouver so that she can learn not to rely on others. Daigo and Ann make it to the post-secondary institutions of their choice while Fuji must repeat his senior year after running away from home.After attending her middle school reunion, Ann spends some time with Daigo, where he tells her to find her own happiness. Six years later, Ann meets a young businessman named Keiichiro Sakura and they become engaged shortly after. After Ann learns that he only uses people for his own gain, she confronts him about his insensitivity, but he is disappointed in her and breaks off the engagement. Almost a week afterward, she takes a train to Okayama, where Daigo teaches elementary school. Ann's grandmother, meanwhile, believes Ann will suffer the same fate as her mother. After a failed suicide attempt on the beach, Ann is taken to the hospital and later meets Daigo, who asks her to marry him. She says yes and at the very end the two are shown to be happily married with an infant son named Ryo. Meanwhile, Fuji decides to marry his cousin Mariko (against his family's wishes) and Shiika decides to work for her uncle in America.