The story begins with a young girl named Annie Clay embarking on a tour of Elvis Presley's famous home, Graceland. Upon returning, she nurtures her ailing mother, who seems to be an avid fan of the King, with food and medication. This routine continues until her mother eventually passes away, followed by a solemn funeral.
Fast forward to the present, where Annie is now a medical student at a hospital. A traumatic incident at the hospital reminds her of her mother, prompting her to drive to the gates of Graceland. She confides to the guard, Gayle, that she has dropped out of medical school. Gayle suggests she become a tour guide at Graceland, and Annie readily accepts the role.
As the news of the caldera in Antarctica breaks and the president's urgent message about an impending apocalypse goes live, Annie and Gayle gather their belongings and useful items from Elvis' house, heading to the basement for safety. Unfortunately, Gayle sustains a leg injury in the process. Three days later, they venture to the roof to assess the situation and witness people fighting in the streets. Over the weeks that follow, an ash cloud engulfs the sun, plunging the world into darkness and freezing temperatures. Simultaneously, Gayle's leg injury worsens due to infection, ultimately leading to her death by Day 46.
The scene shifts to Day 689. Annie is still holed up in the house when she suddenly catches a glimpse of a ray of sunlight — the sun is out again! A group of people approaches the house and discovers Annie, who tries to hide from them. One of the men, Link, enquires about Elvis' cars. While he plays the piano in the house, Annie incapacitates him, steals his gun, and locks herself in a room. Three days later, she is forced to emerge due to hunger, and they offer her food as a gesture of peace.
Link narrates how he survived the ash cloud and how his friend Geiger found him and provided him with sustenance. Geiger is attempting to gather a group of people to safely disable all the country's nuclear power plants. Urkel, another member of the group, explains that the volcano emitted an ash cloud that enveloped the Earth and reduced its temperature by almost 20 degrees. Link estimates that roughly 40% of the US population has perished. He reassures Annie that they will leave soon.
Annie smiles as she watches the group of men play together and even helps reset a fractured bone in Link's hand. Later, she notices that one of the horses she had let loose has returned to the house. One night, Annie goes to the roof and finds Link there. He divulges that he's 25 years old and describes how he and his friends are part of a larger group that aims to restart civilization in the west. However, he warns her about the dangers lurking in Arkansas.
That evening, the entire group sat down for their final supper together. They played a game where Annie had to articulate something she missed from the past and something she didn't. She said she missed giving tours, and they asked her to give one after dinner. By the end of the tour, she and Link were left alone. They drew closer to each other, discussing their feelings of loneliness, and soon Annie was overcome with tears. Link gave her a hug, and they shared a kiss, spending the rest of the night together.
Afterwards, Annie asked Link why they were really there. He revealed that they believed in the existence of an underground city in Colorado, which possessed resources to restart the world. However, they also believed that something dangerous lurked there. He asked Annie to join them.
But in the morning, Annie hid in her room and refused to open the door. Geiger came to fetch Link, telling them that they had a job to do - find the bunker, get inside, and kill "Alex." In the end, Annie didn't go. Later, she found a message from Link in which he promised to come back for her.
A montage showed Annie continuing to live in the house as usual, except now she was pregnant! Months later, she witnessed an explosion nearby and headed out on her horse, thinking it could be Link. Instead, she found a crashed plane and Xavier Collins lying on the ground.
