Buffalo TV news anchor Evan Baxter (STEVE CARELL) has just been elected to Congress, and thus moves to the suburbs of Virginia with his wife, Joan (LAUREN GRAHAM), and their three sons, Dylan (JOHNNY SIMMONS), Jordan (GRAHAM PHILLIPS), and Ryan (JIMMY BENNETT).
On Capitol Hill, the freshman congressman is served by executive assistant Rita (WANDA SYKES), chief of staff Marty (JOHN MICHAEL HIGGINS) and enthusiastic employee Eugene (JONAH HILL). They're all excited when Evan is chosen by powerful committee chairman Congressman Chuck Long (JOHN GOODMAN) to collaborate on a bill, and everything seems to be going his way to fulfill his campaign motto to make a change in the world.
But then God (MORGAN FREEMAN) comes calling, first through a series of seemingly coincidental signs, all of which lead to the Biblical story where God calls on Noah to build an ark. Evan thinks the stress of his new job has gotten the best of him, but when the signs continue and then God finally shows Himself, Evan realizes it's all too serious.
From that point on, and as his hair and beard start growing, animals start arriving two by two, and everyone thinks he's gone crazy or at least is having a severe midlife crisis, Evan starts building the ark.