Newly elected to Congress, former local television news reporter Evan Baxter (Steve Carell) leaves his hometown of
Buffalo, New York and moves to the fictional town of Prestige Crest, Virginia, where his congressional campaign officially declares that he will change the world. Evan prays to God (Morgan Freeman) to give him this opportunity. His wife, Joan (Lauren Graham), also prays that she, Evan, and their three sons (Jimmy Bennett, Graham Phillips, and Johnny Simmons) will be closer together as a family. On the first day of his job at Congress, Evan is given a prime office space, where he is accompanied by his three congressional staffers, Rita, Marty, and Eugene (Wanda Sykes, John Michael Higgins, and Jonah Hill), and invited to junior co-sponsor the Public Land Act bill with his greedy boss, Chuck Long (John Goodman). Soon after Evan’s election to Congress, six strange things start to happen around him:
The number 614 starts to appear everywhere he goes (i.e. alarm clock, government license plate, Rita’s phone extension)
Ancient tools and gopher wood are delivered to his house that he actually did not order.
A man claiming to be the Genesis God appears everywhere he goes.
Pairs of animals simply follow Evan without any apparent reason (with birds even flying into his office through the window).
Evan grows a beard no matter how many times he shaves.
Eight vacant lots in Prestige Crest are purchased in his name.
Evan soon learns that 614 refers to the verse in the Book of Genesis, where God originally instructs Noah to build an Ark in preparation for a flood. God later repeatedly appears in various guises before finally revealing himself to Evan, and cordially insisting that he should also build an Ark as well. God explains to Evan that a flood is coming, and that the only opportunity Evan will have to change the world is by saving his community instead. God also tells Evan to inform others about the flood should they ask him later. Concerned about Evan’s behaviour, Joan initially believes that he is having a mid-life crisis. Evan begins constructing the Ark with his sons, who start to admire him as he is spending more time with them.
Animals eventually follow Evan to Congress. When Long discovers this, he allows Evan latitude at first, but warns him that he will no longer tolerate it if it happens again in the future. Meanwhile, Evan’s staffers are outraged by his change of appearance and behavior. When Evan returns to the Ark during construction, God presents him with a robe, and later tells him that the flood will likely come at midday on September 22. When Joan becomes suspicious of his behavior, Evan tells her the truth: God has been talking to him and is responsible for his new looks and recent actions, although Joan does not believe Evan and she is convinced that he is beginning to lose his mind. After wearing the robe for some time, Evan finds it comfortable, but soon realizes that God will not allow him to take it off and wear anything else after two failed attempts to change his clothes later. The next time Evan arrives at Congress for work, animals follow him once again and he is mysteriously changed into his robe midway during the session. Evan reluctantly explains his divine mission, but Long does not take him seriously, and Evan is suspended from Congress and removed from the Public Land Act bill. Evan deduces that God purposely had him suspended from Congress, so that he would have more time to build the Ark. In continued skepticism, Joan leaves Evan alone after believing that he is going insane.
Evan decides to build the Ark alone, gaining media attention and public ridicule, as hundreds of animals assemble in pairs. Meanwhile, God appears to Joan as a waiter at a diner. God listens to Joan as she expresses concern that Evan is only losing his sanity and allowing himself to become a laughing stock, though claiming that “God told him to do it”. Sympathetic toward Evan, God tells Joan that perhaps it is an only opportunity for them, and explains that he does not give things but only the opportunity by which to obtain things, citing togetherness of families as one of these things. Seeing God’s meaning, Joan returns to Evan with new-found faith and continue helping him finish the Ark together in order to prepare for the flood. Meanwhile, Evan overhears from his staffers that Long has commissioned a dam and has cut corners in doing so, and that he will most likely do the same thing with his Public Land Act bill.
On September 22, Evan loads hundreds of animals onto the Ark in front of hundreds of spectators and live news crews, who continue to mock him. Later, Long and the policemen arrive with a wrecking ball crew to try and destroy the Ark, since it violates numerous building codes in Prestige Crest. Minutes pass with no sign of rain, and while a heavy rainstorm does come, it passes within moments, leaving Evan himself humiliated. However, Evan connects Long’s profiteering ethics and what God had already told him, and realizes that the dam under Long Lake is preparing to burst. Evan warns to those present must board the Ark, and many have do so when the prophesied flood is triggered shortly after the dam burst. Prestige Crest is catastrophically destroyed, and the Ark later rides the flood through the streets and landmarks of Washington, D.C.. The Ark reaches its final destination in front of the Capitol, which disrupts the vote on the Public Land Act bill. Long becomes outraged that the flood did really happen. Evan informs Long that the flood was actually caused by his poor design of the dam, which prompts the other Congressmen also present to turn against Long.
After Congress suspends the Public Land Act bill to investigate Long’s profiteering ethics, and the animals return to their natural habitats, Evan is finally reinstated as a congressman, and celebrates this event by shaving his beard, changing back into his regular clothes, and going on a long-promised hiking trip. When God reappears once again during the hike, Evan is initially disappointed in which he realizes he never needed to build the Ark since the flood had only happened because of Long’s defective dam. However, God reassures Evan that he now has a perfect life as well as everything that he had originally prayed for, and that this would not have happened otherwise. Evan is happy to realize this, and God informs him that the right way to change the world is by doing one Act of Random Kindness (ARK) at a time. During the film’s closing credits, God issues a new commandment to the outgoing audience: “Thou shalt do the dance”. This is later followed by a footage of the film’s cast and crew members dancing to C+C Music Factory’s hit song “Gonna Make You Sweat (Everybody Dance Now)”.