Holly is excited to audition for the Snow Belles, a Christmas-themed pop group founded by her late mother. However, lead Belles singer Marci denies Holly a chance to audition when she shows up late. Nevertheless, Holly takes to the stage and delivers a sensational audition and is upset when Marci passes her over in favor of Staci. Holly is depressed about being turned down, even after her sister suggests she start her own group.

Soon, though, Holly begins to see merit in the idea and decides to ask the manager of the local mall if she can perform at the local Christmas Eve celebration. The manager decides to hold auditions and a competition as a publicity stunt and agrees to let Holly's group into the show. Holly recruits a group of her coworkers including her best friend, AJ, large and lovable Larry, and the shy HR manager, Bernie. They begin rehearsals in the company warehouse. After the second day of rehearsals, AJ says to Holly that he thinks they are doing well, but Holly thinks they need something more.

Later that evening, Holly skids off the road while driving home and crashes into a snowbank. While waiting on a tow truck, she seeks shelter in a nearby tavern and is shocked to discover her boss, the normally uptight and goal-oriented Nick, is a crowd favorite on the karaoke stage due to his energy and stage presence. He sings the song "Burning Love" and wows the crowd . Holly records his performance and uses it to blackmail him into helping her turn the group into solid competition for the Snow Belles. At first, Nick tells that group that he will help, but no one is to know and that they should not consider him a member of the group, too. Eventually, he begins to warm to the group and even joins in performing during rehearsals. It is during one of the last rehearsals where Staci who is hiding in the warehouse, videos the Mistle Tones with Nick singing along. The chemistry between Nick and Holly is more evident and obvious that they are attracted to one another. After the practice Holly invites Nick to join them for a drink at Dickens Tavern, where Holly first saw Nick perform Karaoke. At the bar, AJ, Larry, Bernie and Holly try to think of a name for the band. When she gets home she pulls out the mistletoe that she had removed from above Nick's office door and comes up with the name the Mistle-Tones.

Having seen a video of the group's performance, Marci begins to see Holly as a potential threat and offers her a spot in the Belles to ensure the Mistle-Tones won't compete. Holly confides in Nick that she is considering the offer and begins to tell the others at their office Christmas party. Nick, however, interrupts her by singing "Winter Wonderland" and leading the group in an impromptu performance. Afterwards, Nick tells Holly that the Mistle-Tones are her group and they need her. Holly is just so touched by what he says. She looks up at the mistletoe in the corner and kisses Nick for the first time. She then says that the band needs his help. He says that he is already helping them, and kisses Holly again. She says no what she meant is that the only way the Mistle-tones can win the event is if he sings with them. He says nothing would make him happier. He will sing with the group the following day. However, as Nick is watching Holly get into her car he receives a call from a company executive telling him that he has the promotion and they want him to take over the South Asian division and for him to get on a plane that evening.