On a journey to visit his mother, Jim Riley proposes to his long term girlfriend Bridget. She however, doesn't believe in the concept of marriage, so she turns him down. Stunned by the shock of her refusal, he fails to let his mother know, who's excitedly waiting to celebrate when they arrive. In the knowledge of her son's intended proposal she has hung a giant banner on the front of the house, congratulating them on their engagement!
Jim finds that he cannot bring himself to tell her the truth of the situation. His mother has been suffering depression since the recent death of his father and he doesn't think she'll be able to cope with the bad news. The pretence of their engagement soon leads down a steep slippery slope and Jim's hopes of a weekend of a lifetime quickly turns into complete disarray.
Will the calamitous events of the weekend drive him and Bridget apart, or will the pretence draw them closer together?
"Congratulations" puts the couple's love for one another under the microscope and tests whether it can survive the unexpected...