Plot
The morning of his wedding to Jesse, Ed is revealed to be having doubts, having learned that his fiancée had slept with one of his friends while on a break from Ed. He is cornered before he can escape by Jesse's father, Frank, who begins describing the ups and downs of his relationship with Jesse's mother, Susan.
Years earlier: Frank and Buddy both love Susan. While celebrating New Year's Eve with their friends, Susan resolves to choose a husband that night, and chooses Frank.
Eight years later: Frank is happily married to Susan and they have a seven year old daughter, Jesse. He is a professional speaker who lectures on time management and lives by example: perfectly maximizing his efficiency through scheduling and planning his own life down to the minute.
On the day of an important seminar that could be his major break on the corporate lecture circuit, Susan changes their clocks by ten minutes, to give him time to run a meaningless errand for her, but she moves them the wrong way, causing him to miss the ferry and arrive late to his lecture, which could damage his career. Buddy consoles him in the hotel bar and challenges him to take a chance trying to pick up some attractive women, but he declines. While chatting with Paula, a woman who attended his lecture, she asks if she can use the bathroom in his hotel room due to a phobia of public restrooms and he agrees, only to have her try to seduce him; he resists. Susan calls and he ends the call abruptly when Paula makes a noise, and rushes out, determined to get home. Susan calls back and Paula answers, telling her only that Frank isn't there.
While driving home through the night Frank nearly has a head-on collision with Nancy, a pregnant woman in labor, who misses him only to crash off the side of the road. He drives her to the hospital, where he is asked to fill out some forms. He mistakenly puts his own information down before leaving to resume his trip home. Nancy abandons the baby (having told Frank earlier that she didn't want it) and a nurse calls the number written on her forms trying to reach her.
Frank hasn't yet arrived, and Susan answers the phone, and she learns about the baby. Due to there having been a woman in his hotel room earlier, Susan immediately believes that Frank has been leading a double life, and that it is his baby. When Frank arrives home, she refuses to listen to him and throws him out of the house. Over the next few weeks she refuses to see Frank, or answer his calls, but she does allow him to see Jesse after school.
Frank provides a genetic sample in preparation for a paternity test to prove to Susan that he isn't the baby's father, only to learn that he has Klinefelter's syndrome, which means he is sterile. Initially refusing to believe the results because of the implications, he is finally convinced by the doctor.
Meanwhile, Nancy, having decided to keep her child, brings the baby to Frank's house in hopes of thanking him for his kindness. Finding only Susan at home, Nancy soon clears up the misunderstanding. Susan tries to call Frank to ask him to come home, but Frank has been utterly devastated by the idea of Susan's infidelity and now refuses to take her calls. He eventually confides in Buddy that he isn't Jesse's biological father, to explain why he hasn't gone back to Susan.
Buddy realizes that Jesse is his child, from an encounter with Susan before the night she and Frank got engaged. Believing Frank to be out of the picture, Buddy reveals this to Susan and attempts to win her back, including sending her roses, but she refuses.
After giving a life-changing speech about living on whim at his own time management lecture, Frank decides to live his life based on chance from that moment on. He starts his reformed outlook on life with the simple idea of possibility and randomness by basing his decisions on shuffling three index cards with written options and choosing one at random. After the lecture he sees Paula again and invites her to his room, but he's too drunk to actually perform, and realizes that he still loves Susan.
He returns home, intending to effect a reconciliation, but Susan refuses to tell him who Jesse's father is. While she is upstairs comforting Jesse after a bad dream, Frank sees the roses Buddy sent her, and realizes the truth. He leaves, and plots to kill Buddy. He lures him into a boat which he takes into the middle of the lake, but they both end up falling into the water. Buddy saves Frank and they make it to shore. On the walk back, Buddy admits that Susan doesn't love him; she loves Frank.
Frank realizes that he loves his family; he and Susan reconcile and become a family again.
Back in present-day, Ed realizes that he does love Jesse, and the wedding goes forward. Buddy escorts Susan to her seat, and as father of the bride, Frank walks Jesse down the aisle.
