Jack Campbell (NICOLAS CAGE) is a Wall Street playboy who's about to close a record corporate merger, and expects everyone else at PK Lassiter and Associates, Investment House, such as Alan Mintz (SAUL RUBINEK), to work just as hard on Christmas Eve as he is. At the end of the day, his assistant tells him that Kate Campbell (TÉA LEONI) called, and that sends Jack's mind reeling.
It turns out that thirteen years earlier, Jack and Kate were college sweethearts, and a decision he made to spend a year in London rather than stay with her ended their relationship. Now, Jack wonders if he should call her, but his boss, Peter Lassiter (JOSEF SOMMER), reminds him that old flames are like tax returns that should be thrown into a file cabinet for three years before being cut loose.
As such, Jack doesn't call her and decides to walk home. Stopping in a convenience store on the way, he stumbles into what looks like a holdup, but ends up talking the gunman, Cash (DON CHEADLE), out of doing anything stupid. As they part ways, Cash questions what Jack values in life and then reminds him that he brought all of this on himself.
Not sure of what that meant, Jack goes to sleep, but when he awakens, he begins to get an idea. Instead of waking up in his lavish bachelor pad, he now finds himself in a modest suburban New Jersey home, married to Kate and father to six-year-old Annie (MAKENZIE VEGA) and toddler Josh (JAKE & RYAN MILKOVICH). Horrified at this turn of events, Jack tries to return to his former life, but learns that it no longer exists and that no one from it knows who he is.
Running into Cash once again, Jack learns that he must figure out what all of this means for himself, and tries to discern such info from Arnie Bender (JEREMY PIVEN), his best friend in this alternate universe. Still without any real clue as to what's happened, Jack tries to fit in as best as he can, with only Annie realizing he's not her real father (she thinks he's an alien impersonating him).
As such and despite the lack of sleep, money and high-powered glamour he once commanded, Jack gradually begins to feel comfortable in his new role of the family man and finds himself drawn even closer to Kate than he could have imagined, even considering the amorous attention he gets from their comely friend, Evelyn (LISA THORNHILL), who's obviously attracted to him. When a twist of fate allows him the chance to return to his old life, he must then decide which lifestyle will ultimately be better for him.