Two resentful exes must awkwardly spend Christmas together after they learn that their new partners are siblings.
Avery and Logan haven't spoken in the 10 years since they broke up. As Christmas approaches, they discover that their new partners are siblings, and both of them have been invited to stay with the family for the holidays. Avery proposes that they keep their past a secret to avoid any awkward confrontations, but hiding the truth turns out to be more difficult than it seems--and spending time together reignites old sparks.
Connected from childhood, Avery and Logan transitioned from close friends into a couple over their 18 years. When she readily accepts an opportunity to work in England, Logan almost proposes at her farewell party, fearing he might lose her. Avery breaks up with him, uncomfortable with the pressure.
Ten years later, Avery and Logan inadvertently see each other next as they each are meeting their significant other's family at Christmas, as their partners, Cam and Cassie Morgan, are siblings. Mortified, Avery convinces Logan to keep their past secret, fearing awkwardness, especially with the hostile matriarch Erica.
As the Morgans sit for their annual family portrait, Avery and Logan seek the tree. Knowing her expertise with business proposals, he requests her help with a architecture proposal due shortly. In exchange, Logan will help her connect with the Morgans.
On their return, the hungry Avery unknowingly eats THC gummy bears from the youngest Morgan Callum's coat pocket. When Logan realizes, he tries to cancel the reading Avery volunteered for to impress the Morgans at 4 p.m. mass.
Although the edibles effects kick in just as Avery is called to the altar so she cannot focus, she improvises. Hallucinating that the Mary statue is encouraging her, she tries to tell the Bethlehem story by reciting Kool & the Gang's Celebration. Initially met with silence, someone chimes in with the next line, and everyone joins in.
The priest thanks Avery for motivating the congregation, as some of the children want to return soon. That evening, due to munchies, Avery wolfs down Erica's prized cookies then falls asleep on the counter. Upon waking, she has Logan distract Erica so she can frame the dog. The panicked Erica insists on rushing the mini dog to the vet, as chocolate is poisonous for them.
Avery takes them to the vet. Feigning concern for her, Avery offers to aid the doctor. Once alone, Avery admits her guilt to the vet, begging him to keep her secret. When the fake procedure is done, she pays the over $1,000 bill for his silence.
Returning to the house, they describe the vet "ordeal", so Avery comes across as a hero. Logan privately scolds her for risking their secret by lying about the cookies, Callum follows and hears everything. He takes her number, promising to contact her.
In the evening, the two couples go out together and soon, Cam's ex Sophie joins them. Avery is called by her dad's real estate agent, seeking the house key. When she tells everyone, the sober Logan offers to take her on the long drive.
In her childhood home, Avery commiserates how much she misses her mother, so Logan gives her support. On their drive back, Callum's second blackmail call reroutes them to pick up the teen, drunk from the alcohol they had bought for him. Back at the house, Logan throws himself into the project proposal. Working into the night, he sees Cam's 5 a.m. arrival, then is asked to lie about the arrival time, presumed because he was with Sophie.
At Christmas Eve dinner, there are multiple revelations. Just as Avery and Logan are revealed to be from the same small town, Sophie announces she is moving back. Logan accidentally finds Stan's wife, Marge, and Erica's husband, Leonard, in a closet, so is asked to not divulge their affair.
As Secret Santa gifts are opened, gifts get switched. Then, as Avery and Logan are scolding Callum in another room, Logan's mom and grandmother show up by surprise. He warns his mother to pretend to not know Avery, but the senior quickly exposes the exes. Soon Callum exposes Avery's lies, then Margaret and Leonard's affair is revealed, a surprise to everyone except Erica.
Avery's father, Mitchell, returns from his trip. He surprises her with the house key, providing she really buys it, as Logan told him she wanted it. Avery, in turn, pushes Erica to give Stan Logan's proposal. He hires Logan upon recognizing they share a vision.
At Avery's house-warming, Logan asks her for another try, as he believes they could make it. They say they love each other and kiss. A year later, they are planning their wedding while living together. Logan's boss, Stan, drops off a tin of cookies before meeting with the Morgan's kids with his new love, Erica. It is revealed Avery and Logan get married sometime later on.
