Dylan Bernard and Emma Leroy, 25, are wildly in love and want to spend their life together. The only problem is that their parents know nothing about it, and for a good reason: Dylan is the son of Krystel Bernard, a union representative and arch enemy of her boss Etienne Leroy, a powerful corporate executive in northern France. Dylan and Emma plan a family ski vacation to break the news to their parents that they're going to get married.
After announcing the engagement, Dylan and Emma do their best to calm down the uproar in their respective families. Despite their efforts, things don't go as planned. The war between Krystel and Etienne reaches new proportions during the ski trip.
The Leroys, accompanied by their daughter Emma, eight months pregnant, and her partner Dylan, return to the mountains of Les Gets for the funeral of Garcin, the owner of Chamois ski resort. But as they arrive at the church, Emma's water breaks and she is about to give birth. To complicate matters, a local event, the "Gets Wine Show", blocks them from getting to the hospital. Emma has to give birth at Chamois with the help of two firemen.
A few hours later, Etienne and Marie-Odile welcome their granddaughter into the world. The parents haven't decided upon a name yet.
Emma and Dylan's differing social backgrounds make them disagree about how to name their daughter. The choice gets even tougher when the grandparents put their two cents in.
For Etienne and Marie-Odile, nothing less than an elegant, traditional name will do. They dream of having their granddaughter named Victoire, after the grandmother of Etienne, who loves telling the story about what an extraordinary woman she was - a WWI hero.
Dylan's parents Krystel and Thierry, who have rushed to Les Gets to be with their son and newborn granddaughter, propose the name Kelly. That's about the only thing the couple has agreed upon for months, having recently separated. Krystel is convinced that Thierry cheated on her.
The war between the Leroys and the Bernards has escalated to new heights since Krystel started a strike at the factory, suspecting Etienne of being in negotiations to relocate to China. Meanwhile, Marie-Odile is convinced that her husband is hiding major problems in his business. Planning to get a job herself, she is having her work skills professionally evaluated and is waiting for the results.
Caught in the crossfire between their parents, Emma and Dylan start to argue, too.
Cutting everyone else out of the picture, Dylan selfishly registers his daughter under the name of Kelly, according to his parents' suggestion, instead of Victoire, like the Leroys wanted.
Ashamed of lying and racked with guilt, Dylan willingly, even eagerly, accepts when the Leroys propose getting his daughter baptized.
But when Etienne goes to city hall to get a copy of the birth certificate for Father Cyril, in charge of the baptism, he discovers that his granddaughter has been named Kelly.
Etienne's anger towards Dylan is only equalled by the disappointment of the Bernards when they find out their son has agreed to a baptism. The Bernards don't get baptized, and as a matter of principle, never set foot inside a church!
Attacked on all sides, Dylan finds comfort in Emma, who forgives him for choosing the name of Kelly. She is aware of the fact they are both being eaten alive by their families. In the end, they decide to give their daughter the name they have both always wanted from the start: Ainoha.
In the same spirit of teamwork, they have an ingenious idea to bring their families together: organize a "double baptism" with two ceremonies, one religious and one secular.
Positive point: Etienne and Krystel try hard to outdo each other's initiative and creativity, one for the religious rite, the other for the secular event, knowing both will be celebrated on an exceptional basis at Chamois.
Negative point: the double baptism ends up deepening the divide between the two families instead of bringing them together, especially with Krystel continuing to remotely organize her strike at the Leroy factory. Meanwhile, Thierry and Marie-Odile desperately hope that someday their spouses will treat each other with respect.
Left alone, Thierry begins to imagine life as a divorced man, and possibly starting a new life with another woman. Marie-Odile, for the first time in her life, has a job. Thanks to Patrick, mayor of Les Gets, who also happens to be a doctor and her ex-boyfriend, she has found temporary work as a salesperson at the village's gourmet food boutique.
The two baptisms both turn out to be lovely, solemn ceremonies. But as soon as they are over, Patrick the mayor announces bad news. Little Ainoha's blood test has revealed a probable genetic disease. Though relatively benign, it requires everyone in the family to get tested, beginning with the grandparents.
That night, consumed with worry, Krystel and Thierry break down and make love. Meanwhile, Marie- Odile and Etienne anxiously prepare to reveal a secret to their daughter.
Emma can't get over the fact that her parents have been lying to her for twenty-five years. Not only does she learn that Etienne is not her biological father, but she finds out that her real father is Father Cyril, the local parish priest, the same man who baptized her daughter yesterday! Horrified by her parents' dishonesty, Emma decides to stay away from them and impetuously declares that she is quitting medical school. And to top it off, she informs them that Dylan isn't a doctor like she has always led them to believe - he's a cook!
Everyone is so preoccupied with the Leroys' paternity issues, no one has noticed that the younger kids have disappeared.
With the help of Jessica's boyfriend Maxime, Kevin and Thomas have gone on a snow mobile race at night for the sole goal of impressing Chloe. Kevin has a crush on her.
But after they run out of gas, Kevin, Chloe and Thomas have to wait in the cold until morning. When local police bring them back to Chamois half-frozen, they get scolded and have to make up for it by shoveling snow in the village all day long.
While Etienne gets severely depressed about his relationship with his daughter, Emma goes to see her real father: Father Cyril. Despite her fears, everything goes well and the priest agrees to do a blood test for Ainoha.
Relieved that she is no longer living a lie, Emma decides it's time for her and Dylan to start a new life. There is a restaurant for sale in Les Gets - why not buy it? It's Dylan's dream.
Needless to say, the decision makes the Leroys furious. They are determined to convince their daughter to go back to medical school, even if it's against her will.
Through Patrick the mayor, Marie-Odile and Etienne obtain an emergency appointment with the dean of Chambery Medical School. And thanks to Marie-Odile's vivacious powers of persuasion, the dean agrees to once again register Emma as a medical student. Perfect timing: Dylan has just convinced Emma to continue her medical studies. Everything seems to be falling back into place, until Father Cyril comes to Chamois with the results of his blood test. He is not Emma's biological father, after all.
The Chamois resort is thunderstruck by the revelation: if Father Cyril isn't Emma's biological father, Marie-Odile conceived her with another man, which means she must have cheated on Etienne 25 years ago.
Even so, Marie Odile swears to high heaven that she didn't have a lover. Her protests don't convince anyone: not Emma nor the Bernards, and least of all Etienne.
Humiliated, betrayed and hurt, Etienne leaves her right then and there and returns to Paris. His departure is bad news for Krystel, whose co-workers have accidentally caused a fire while searching his office. If Etienne goes back now, everyone is going to get fired.
Left alone at Chamois, Marie-Odile gets depressed. But Thierry shows his empathy and extends a hand to help her understand what happened 25 years ago. If his calculations are correct, Emma was conceived in late December 1992. To take Marie-Odile back in time, Thierry proposes a hypnosis session. Though far from being a hypnotherapist, he claims to have learned a thing or two from the sessions he did to stop smoking.
And it works! Well, almost. Marie-Odile definitely goes to sleep during the session, but she wakes up convinced that Emma was conceived during the big New Year's Eve party right there in Les Gets, 25 years ago.
With the help of Dylan, Thierry and Marie-Odile go on a quest to find any possible progenitor who was at that famous party, starting with the mayor, her ex-boyfriend Patrick. But they come back stumped. Marie-Odile is desperate and sad. She hasn't heard a single word from Etienne.
Little does she know that he isn't so far away - just a mile or two down the road at a hotel. At the last minute, wondering if he could actually be the biological father himself, he came back to Les Gets to get a test done at the lab.
The results are surprising: Etienne isn't the father, but it could almost be him. It has to be a close member of his family. Etienne remembers he has a long-lost brother: Michel, his twin, a hermit who lives way up in the mountains. He sets out to find him and bring him back to Chamois, where Michel admits to having stolen his brother's identity during that famous New Year's Eve party back in 1992. Everybody goes to the lab with Michel, leaving only Krystel behind to take care of Ainoha and the hotel. While the teenagers put on a little party, Michel and the group get into an argument with two police officers and they all get arrested.
When they are released in the morning, Etienne, Marie-Odile, Thierry, Emma and Dylan find the Chamois resort in a terrible mess. Krystel lies unconscious on the floor and Ainoha has disappeared.
The Bernards and the Leroys, in a panic, search everywhere for Ainoha. Luckily, Thierry finds the Babyphone and hears the infant cooing on the other end.
After searching in every nook and corner, they finally find the baby in the attic, brought there by Jessica to protect her.
Though Ainoha is safe and sound, Emma is furious with Krystel for not taking care of her child. Feeling guilty and ashamed, Krystel isolates herself from the others. Etienne catches up with her and befriends her. What happened in the hotel the night before is beyond her responsibility: the teens threw a little party that turned into a huge bash when it got out on social media.
As they exchange kind and peaceful words for the first time in their lives, Krystel and Etienne simultaneously receive phone calls from the factory. Krystel's coworkers were caught red-handed in the office of their boss, which they were trying to fix up after accidentally setting it on fire.
Krystel and Etienne immediately leave Chamois. He is out to fire Krystel's union buddies, and she is out to save them.
Marie-Odile and Thierry find themselves alone with the duty of dealing with the teenagers. They've got to punish Kevin, Thomas and Chloe for putting on the party, and Jessica for taking advantage of the chaos to spend the night with Maxime.
But Kevin, negotiating to reduce their punishment, offers proof of what really happened that night. He shows them the hotel's video surveillance camera footage. Marie-Odile and Thierry, stupefied to see how crazy the party got, see Krystel looking overwhelmed as she takes what she thinks is an aspirin but turns out to be drugs. Thierry is happy to be able to reassure his wife that it wasn't her fault, but he can't get a hold of her. Back at the factory, it's cold war again between the union rep and her boss. Krystel threatens to tell everybody about Etienne's plans to bring foreign investors into the company's capital. Etienne threatens to tell everyone that Krystel has been vacationing with her capitalist boss! They finally manage to come to an agreement and Krystel saves her co-workers' jobs. They leave together to return to Les Gets. Unfortunately, because of an accident along the way, they are forced to spend the night in a crummy little hotel and share a room. Just a few miles away, in Les Gets, Marie-Odile and Thierry wait up and chat, not knowing their spouses are sleeping together nearby, in the same bed. Thierry shares his lingering doubts about his relationship with Krystel, while Marie-Odile tells him about the results of her work skills evaluation. Verdict: she has the profile of an artist!
Marie-Odile and Thierry are woken up by Lucille, owner of the Chamois resort, who has come back to show the hotel to potential buyers. Furious to find it in an unspeakable state, she throws everybody out, but soon changes her mind. It's December 24 and the idea of leaving two families and a newborn baby out in the cold makes her feel too guilty.
When Etienne and Krystel finally get back to Chamois, they are welcomed by Marie-Odile, who informs them that their first Christmas together there as grandparents will also be the last they spend there, since the hotel is up for sale. And since that makes two major events in one, Marie- Odile wants to have a grand Christmas party worthy of the occasion, in the spirit of friendship and love.
A spirit soon thwarted when Krystel discovers a message on Thierry's phone: the woman she suspects him of cheating on her with has just sent him a suggestive photo with warm wishes for the new year. It's more than enough to start the war between them all over again, especially when Thierry weakly admits that he did actually kiss her "a little"! Thierry confides in Etienne the whole afternoon. Sent out by Marie Odile to get a Christmas tree, it takes them a ridiculous amount of time to find one, because there just aren't any left on Christmas Eve! Etienne and Thierry are going to have to uproot a tree in the forest, which is of course completely illegal.
Meanwhile, back at Chamois, Christmas starts to seem more complex and less friendly than expected. Krystel doesn't know if she can bear to sit at the same table with Thierry, Kevin wants Chloe to stay with him instead of meeting her father in Geneva, Jessica hides Maxime in the attic, hoping she will be able to spend a whole night with him, and Dylan is worried that his cooking won't be good enough for a fancy holiday dinner!
Marie-Odile is hard at work on all fronts, decorating Chamois and trying to get Krystel and Thierry to make up.
As the evening begins, anything is possible but nothing will go according to Marie-Odile's ideal plans.