The novel is divided into four parts—"Hanger Town", "Non-Negligible Probabilities", "Wishful Thinking", and "Soon, They Will"—each containing five chapters, and an epilogue. Each part has an introductory graphic giving the date, and the asteroid's right ascension, declination, elongation and delta, or distance from Earth, in astronomical units. The first part is dated March 20; the epilogue, April 11.
Background
In April 2011, astronomers discover a new asteroid, 2011GV1. Analysis of its unusual orbit shows that it may come very close to Earth soon. By August, not only is that likely, the probability of an impact reaches five percent, triggering an economic panic that results in the bankruptcy of prominent corporations including McDonald's, 7-Eleven, Dunkin' Donuts, and Starbucks. Panera persists but their founders have undergone a cult-like religious rebirth and staffed them with people who share their beliefs.
As the asteroid, now popularly named Maia, approaches, its diameter is measured at 6.5 kilometers (4.0 mi), large enough to cause serious planetwide effects and the likely end of civilization should it strike the Earth. The probability of impact is regularly revised upward, peaking at 53 percent before Maia goes in conjunction with the sun and is unable to be seen for four months. In the face of increasing instability caused by the anticipation, governments enact strict emergency laws. The U.S. Congress passes the Impact Preparation Security and Stabilization Act (IPSSA), banning trade and production of firearms, imposing wage and price controls, and legalizing marijuana while toughening penalties for the possession or distribution of other drugs.
In January 2012 Maia emerges from conjunction with the sun and astronomers are able to determine whether the chances are 100 percent or zero. A tearful NASA astronomer announces to the largest television audience in history that Maia will indeed collide with the planet on October 3, 2012. It is determined that this will be impossible to prevent. Social and economic order begins to collapse as people leave their jobs to do things they will never have a chance to again (known in the book as "Bucket Listers"), and many commit suicide. Oil imports cease and the U.S. is limited to the Strategic Petroleum Reserve. After commercial supplies run out, only the police and military have fuel supplies, and civilians respond by converting their vehicles to run on biodiesel.
Synopsis
In late March 2012, Henry Palace, a young detective with the Concord, New Hampshire police, is called to a crime scene: a man named Peter Zell has apparently hanged himself in the men's room of a former McDonald's. The case seems clear-cut, but Palace wonders about the bruises on Zell's head and the fact that he was wearing a cheap suit but used an expensive belt to hang himself. Palace decides to consider the death a possible murder, and to investigate despite the limited resources available and peer pressure not to waste them.
His investigation finds several odd loose ends. Zell was an actuary who worked at an insurance company; the previous year he stopped showing up to work for several weeks before returning with no explanation, and his boss recalls an out-of-character angry incident at the office Halloween party. His secretary, Naomi Eddes, says she wasn't close to Zell, although Palace saw her in the parking lot outside the McDonald's. Zell's co-workers say he left that night with a man in a biodiesel-operated pickup truck. At Zell's apartment, Palace finds a stack of newspaper clippings about Maia, with extensive mathematical calculations in the margin, and the unexplained label "12.375". Zell had begun writing a note to his sister, Sophia Littlejohn, a midwife, but had stopped after addressing it. At Sophia's house, her husband Erik tells Palace that Zell was lately very depressed, but lies about his wife's whereabouts. The coroner refuses to do more than the absolute minimum when autopsying Zell's body, but Palace takes a vial of Zell's blood to the toxicology lab anyway.
Meanwhile, Palace must also deal with his sister Nico, who asks him to try to find her worthless husband Derek, who has gone missing. Eventually Palace learns that Derek was arrested for driving an ATV onto closed military property. He is able to visit Derek in detention, but Derek will not speak to him and Palace cannot secure his release.
Palace finds the driver of the pickup truck, a friend of Zell's named J.T. Toussaint, but his story that Zell left his house later that evening after the two saw a movie and drank some beers checks out. A patrol cop from the crime scene has been following the trail of Zell's cell phone, which was stolen from his body, and recovered it. Palace finds that Zell called Naomi Eddes every night, proof that she was lying to Palace earlier. When he confronts her, she explains that Zell was addicted to morphine and needed her help getting clean. Palace conjectures that the "12.375" on Zell's box is a percentage—that is, the threshold at which the chance of Maia destroying the Earth became high enough that it would be worth attempting a risky thing he'd always wanted to do: experimenting with drugs.
When a computer check finds that Toussaint is the son of a onetime major local drug dealer, Palace returns to question him. Toussaint admits to helping Zell use drugs but not to supplying them; Zell brought his own morphine sulfate to Toussaint's house, and Toussaint insists he doesn't know where it came from. When threatened with arrest, Toussaint tries to escape, injuring Palace's eye, and is then fatally shot by one of the other detectives. While his injury is being treated, Palace learns that midwives can write prescriptions, and realizes that Zell must have stolen his sister Sophia's prescription pad. He confirms this in a meeting with Sophia. She discovered the theft and got her prescription pad back from her brother in October, which accounts for Zell's strange behavior at that time: he was having withdrawal symptoms. Sophia admits that she hadn't told Palace about it because her husband wanted it kept quiet.
On behalf of his sister, Palace reaches out to Alison Koechner, a former high school girlfriend who now works with the Justice Department. Palace travels to Boston to see her, and from what she says Palace realizes that Derek believes in a conspiracy theory that claims the government is hiding information about the asteroid and some measures it has taken to ensure the survival of certain elites. Palace finds people's denial of the coming catastrophe more depressing than the catastrophe itself. Alison suggests that there was no good reason for Toussaint to attempt a risky escape unless there was something else in his house. Palace searches Toussaint's house and finds a large stash of drugs, guns, and cash hidden in the doghouse; while he is there he hears someone else flee the scene.
Naomi Eddes calls Palace with an idea: with no actuarial work left to do, Zell, like everyone else at his company, was investigating life insurance claims. Someone who had collected on a false insurance claim would have a motive for murder (in order to avoid spending all the time left before the world ends in prison). Palace and Eddes have dinner and she spends the night at his apartment, then leaves early in the morning. The toxicology screen on Zell's blood comes back and finally proves that Palace was right to suspect murder: prior to his death, he had been drugged with GHB. Nico calls and quickly tells her brother she will be leaving for a long time but that she will see him again, then hangs up. Palace drives to the military base where Derek was detained, but the soldiers deny that Derek was ever there. Just after that, Palace learns that Naomi has been found in her office, shot dead, apparently while searching for a file she promised to get him.
Palace calls Naomi's father to deliver the news, but as soon as he identifies himself as a police officer, the father hangs up. From the father's behavior Palace guesses that Naomi has a history of trouble with the law, and he has a toxicology screen run on her blood: it reveals morphine sulfate. Naomi was an addict herself, which is why Zell came to her for help with his own withdrawal. From this Palace puts it together: Naomi had started using drugs again when the news about the asteroid was confirmed; she got her drugs from Toussaint, having learned about him from Zell. The insurance-fraud suggestion was a red herring. Zell and Eddes were both killed by Toussaint's supplier: Sophia's husband, Erik Littlejohn, who has been stealing the pain medications from the hospital where his wife works. Palace arrests Littlejohn and takes him to the station house, where the detectives are told that the department has been federalized and is being shut down.
In the epilogue, Palace, who has now been granted early retirement, bicycles to the New Hampshire shore. Since the case was closed it has been announced that Maia will hit Indonesia, far away from the U.S. With the chances of post-impact survival a little higher, at least in the short term, the public mood is less gloomy. At the beach, he tidies up one loose end from the case, then returns home, where he finds his sister waiting for him. She confesses that she used both Palace and Derek to help a group she was part of determine whether the military facility her husband was held in was in fact the one where they believe the government is working on its plans for a lunar habitat, and then leaves.
