[from wiki] Plot summary
Captain Caleb Holt (Kirk Cameron) is a firefighter in Albany, Georgia who holds the motto "Never leave your partner behind". Meanwhile his relationship with his wife Catherine (Erin Bethea) suffers to the point that she wants a divorce.
Caleb and Catherine both complain to their respective friends about how it is the other one’s fault that their relationship is deteriorating. Among Catherine’s complaints are Caleb’s addiction to internet pornography and a large sum of money ($24,000) he has saved up for a fishing boat he intends to buy, ignoring the fact that Catherine’s disabled mother is in need of hospital equipment that she cannot afford, and which insurance refuses to cover. When Caleb tells his father, John, about the impending divorce, John challenges Caleb to commit to a 40-day test which he calls the "Love Dare", based on Alex (the film’s director) and Stephen Kendrick’s book of the same name, which Caleb agrees to try. Initially Catherine doubts Caleb’s sincerity in his attempts to win her back due to his half-hearted attempts at completing the Love Dare, but Caleb continues with encouragement from his father and his close friend Michael (Ken Bevel), who also encourages him to become a born-again Christian.
In the meantime, Catherine begins flirting with Dr. Gavin Keller (Perry Revell) at the hospital where she works (who does not know that she is married because she is no longer wearing her wedding ring), informing him about her mother’s medical situation. Around this time, Caleb is injured while rescuing a girl in a fire and is brought to Catherine’s hospital, where a nurse inadvertently says in front of Dr. Keller that Caleb is Catherine’s husband.
As he continues his 40-day challenge, Caleb begins doing more household chores and running more errands for Catherine, and he even leaves her roses. Caleb also smashes his computer to pieces with a baseball bat in order to remove the temptation of viewing internet pornography. Nevertheless, Catherine is still intent on divorce.
Catherine later learns that the equipment needed for her mother’s medical care has been payed for in full. Assuming that it was Dr. Keller, she arranges a lunch date with him. Caleb informs Keller that he will not let him have Catherine without a fight, at which point Keller breaks off his relationship with Catherine and it is revealed that he is also married.
Caleb later finds Catherine at home sick, and decides to take care of her. At this point she asks Caleb why he has changed his behavior, and he mentions "The Love Dare". Caleb then fully apologizes to Catharine for his past selfishness.
Days later, Catherine learns that it was Caleb, not Dr. Keller, who purchased her mother’s medical equipment. At this point she becomes convinced that his desire to change is sincere, and decides to remain in the marriage. The couple then renews their wedding vows in an outdoor ceremony, this time as a covenant with God.