She's a kind hearted, sweet, lovely, sensitive and friendly woman.
In 1983, young Catherine always dreamed of marrying a man like her father. She asks, in a child's innocence, if she could marry her father.
Her mother tells her no, that he is already her husband and their love will never be done; Catherine could have her happily ever after when she found someone who truly cares for her.
Twenty-five years later, Catherine is a hospital administrator and married to fire captain Caleb Holt. Caleb recruits young men under the dictum of never leaving one's partner, especially in a fire.
But at home, it is revealed that he and Catherine argue over almost everything. Later, Catherine accuses Caleb of being selfish with his time and money and is especially angered that Caleb is saving up his money to buy a large and expensive boat.
Caleb retorts that Catherine prioritizes preferences over needs and is ungrateful for all he does to help others. They both feel that the other is uncaring and unappreciative of the other. Their constant arguing finally comes to an end and Catherine demands a divorce which an enraged Caleb agrees to.
The two complain to their respective friends, showing the depth of their miscommunication. Caleb's father John convinces his son to hold off on divorce proceedings in order to try the Love Dare, a 40-day challenge for improving marriages by changing the way a spouse is treated.
Caleb reluctantly agrees, though he decides not to tell Catherine. At the hospital where she works, Catherine has been openly flirting with a doctor named Gavin Keller whom she is attracted to, because he treats her kindly and with respect.
The Love Dare begins and it introduces new concepts each day. Caleb completes each task, albeit halfheartedly, seeing it more as a checklist than an actual investment.
The nurses at Catherine's hospital warn her not to trust him, thinking that he is merely trying to "butter her up" for a better divorce settlement. Additionally, she dismisses his attempts because he chooses internet pornography over intimacy with her, making her feel humiliated and inadequate.
With encouragement from his father and Michael, Caleb forges ahead anyway, though Catherine grows closer to the doctor while Caleb struggles through each day. After going all out on Day 19 with a candlelit dinner, Catherine tells Caleb directly to his face that she doesn't love him anymore, prompting him to almost quit.
John tells his son that he needs to accept Christ into his life, and emphasizes giving love and forgiveness to a partner, whether it is deserved or not.
Sometime later, during a rescue, Caleb sustains first-degree burns and while he is being treated at the hospital where his wife works, Dr. Keller inadvertently discovers that Catherine is married, but continues his affections anyway.
Invigorated by his faith, Caleb asks God for help in defeating his demons and overcoming his addictions. He destroys the computer containing the pornography and places extravagant flowers in its place, along with a note saying that he loves his wife more.
Despite the genuine act, Catherine replies with an envelope containing a petition for divorce, leaving Caleb heartbroken.
Many years earlier, Catherine's mother survived a stroke, but a side effect left her partially paralyzed and unable to speak, necessitating medical treatment and equipment.
Catherine goes to see the electric wheelchair and bed (which costs $24,300) needed for her mother, and discovers that it has already been paid for in full.
She assumes Dr. Keller footed the bill, driving them closer together. Caleb eventually discovers this burgeoning affair and confronts the doctor about it.
Caleb firmly states that he will not step aside and will continue to fight for her heart too, while thanking the doctor for treating his injuries.
After Caleb leaves, the doctor pulls out a wedding ring, revealing that he is actually married himself and ends his affections towards Catherine.
Caleb and Catherine continue about their lives and Caleb follows through on the Love Dare, until one day Catherine discovers the book. While taking care of a sick Catherine, Caleb reveals that he has already passed the 40 days, but does not care, as he now wants to show unconditional love for Catherine.
He gives a heartfelt apology for the way he has treated her over the past few years and promises to be a better husband to her in order to live up to the same principle that he teaches his men: never leave your partner.
While she takes time to think about the divorce, Catherine discovers that Caleb used his entire life savings to buy her mother's bed and wheelchair while Dr. Keller only contributed $300.
Moved to tears by the profound selflessness of his act, Catherine and Caleb reconcile, resulting in a passionate kiss. Caleb also discovers to his great surprise that his mother, whom he has treated poorly, once used the Love Dare on his father, and not vice versa as Caleb had originally thought.
The film ends with Caleb and Catherine renewing their wedding vows as a covenant with God. The last shot is of the wedding cake, topped with the salt and pepper shakers Michael glued together.