Paul Conroy (Ryan Reynolds), a US truck driver based in Iraq, awakens buried alive in a wooden coffin, bound and gagged, with only a Zippo and a BlackBerry. Although he initially has no idea how he got there, he soon starts to piece together what has happened to him. He remembers that he and several other trucks were ambushed by insurgents, who killed the other truck drivers. After finding the cellphone, Conroy attempts to contact his wife and employers, but is able only to leave a message for both of them. Paul is able to contact the FBI, but they cut off before he can explain the situation. Conroy’s kidnapper phones him and demands a ransom of $5 million to release him alive, which is later lowered to $1 million.
Conroy eventually gets into contact with the State Department, who pass him onto a hostage rescue group led by Dan Brenner (Robert Paterson). Brenner tells Conroy they are doing their best to find him; however, Conroy is not convinced and asks Brenner to name a person who they had saved before. Brenner tells him they saved a man called Mark White three weeks ago. The kidnapper calls Conroy back and demands he make a ransom video, which he refuses to do. When the kidnapper threatens to kill his kidnapped co-worker, Conroy reluctantly agrees to do the video. While Paul is waiting on his kidnapper to respond to the video, he awakes to find a snake has made its way into the coffin. He uses his flask, filled with alcohol, and the lighter to set fire to the area where the snake is and the snake escapes through a hole in the coffin, and Paul barely has time to put the fire out before the overturned flask can ignite. After completing the ransom video, Conroy receives a video from the kidnapper showing the female employee he knew being shot in the head. Shortly afterwards, there is a violent shaking in the coffin, and sand starts to leak into it.
Later on, Conroy receives a phone call from his employers, who inform him that he was fired from his job that morning due to fraternizing with the same female employee and so if he dies, his family will not get any insurance money. Conroy states the two were just friends however his pleas are ignored. Brenner calls and explains that some F-16 fighter planes just bombed the area the coffin is in, even though they knew Conroy was in the area. Conroy begins to lose all hope and does a last will and testament in video form, giving his son all of his clothes and his wife his personal savings of $700. As time goes on the kidnapper calls with demands for blood instead of money and tells Conroy to cut his finger off and send a recording of it. The kidnapper lets Conroy know he has his home address, and states he will harm his family if he does not make the video however he will not harm his family and will tell the US government where Conroy is if he complies. Conroy films himself cutting off one of his fingers and sends the video.
Within a few minutes, Brenner calls saying they now know where he is, explaining that they were given details of where to find a man who was buried alive by an insurgent. Conroy receives a phone call from his wife and tells her he is going to be okay, and they express their love for each other. A few minutes later, Brenner calls saying that they are close and have found his location. They arrive at the apparent burial site and are about to dig up the coffin. Through the phone, digging is heard, but Conroy cannot hear digging around him. Sand begins to fill the coffin to dangerous levels, giving him seconds to live. When the group digs up the coffin, it turns out the insurgent led them to Mark White, the man Brenner earlier in the film claimed had been rescued. Paul hears his final words, that of Brenner saying over the phone, “I’m sorry, Paul. I’m so sorry” as the coffin fills with sand which eventually kills Paul as he tries to calm himself down.