A 70-mile-wide asteroid is en route to Earth, and the last best attempt to counter it has failed. Also failing is the marriage of soft-spoken insurance salesman Dodge (Golden Globe Award winner Steve Carell); the breaking news that the world will end in an estimated 21 days cues his wife to leave him on the spot. Dodge is a man who has always played by the rules of life, while his neighbor Penny (Academy Award nominee Keira Knightley) is an extroverted woman who hasn't. From these opposite perspectives, both initially choose to navigate the impending end of the world with blinders on. Dodge declines joining his friends in increasingly reckless behavior, while Penny fixates on her relationship issues with a self-absorbed musician. The two misfits meet first when Penny has a rough night and then again when she belatedly delivers Dodge a lost letter. That letter could alter Dodge's future; it's from his high-school sweetheart Olivia, the love of his life. When a riot breaks out around their apartment building, Dodge realizes that he must seek Olivia out before it's too late while Penny makes the decision to spend her last days with family in England. Seizing the moment, Dodge promises to help Penny reach her family if she will provide transport for the two of them in her car immediately. She agrees, and they escape. On the road together, the unlikely travelling companions' respective personal journeys accelerate, and their outlooks - if not the world's - brighten.